Regeneration, i.e. the replacement of lost body parts by new outgrowths or by remodelling existing tissues, has been studied for centuries. However, in recent years important developments took place in this field too, owing to new soph isticated techniques and to novel theoretical concepts. Advances in Molecular Genetics, Biochemistry, Cell and Neurobiology, Immunology, to mention a few of them, are the main causes of this resurgence of interest in regeneration. As a consequence, more and more meetings and pUblications are devoted, either exclusively or for a large part, to basic and applied research of regenerative processes. "Regeneration ists" scattered in laboratories allover the world and accus tomed to know each other through exchange of reprints - occa sionally an encounter in a large conference - tend now to form small groups, even societies and to institutionalize their meetings. Although the critical mass of scientists involved in regeneration research does not seem yet to be reached, for an autonomous development of this sector, regular and frequent meetings of experts appear useful, even necessary. Such a meeting was convened in Saronis, near Athens, Greece, from 19 to 23 September 1988 and sponsored by the NATO Science Committee and the University of Athens. The present volume contains the contributions to this Advanced Research Workshop on "Recent Trends in Regeneration Research". About 50 biologists from different countries, either mem bers of the Alliance or outside it (U.R.S.S., India, Egypt, Switzerland, Sweden) took part, mostly as invited speakers.

The German land of Hesse (Bundesland Hessen) is well known for its excellent wines (Rheinhessen), for its financial centre and for its airport (FrankfurtlMain). It is, unjustifiably, far less well known for its importance to thennoregulation. Within the small area of Bad Nauheim, Giessen and Marburg (in alphabetical order) a greater concentration of students of thenno regulation has been trained or worked or is working than probably in any other single area of Europe, if not the world. It is thus most appropriate to hold the Ninth International Symposium on the Pharmacology of Thennoregulation in Giessen, from August 7 to 12, 1994. The community of students of thennoregulation was extremely grateful that Professor Kurt Bruck and the lustus-Liebig-University of Giessen had extended this invitation. The same community was even more saddened that Kurt Bruck died on April 27, 1992 and thus could not participate in this event that had been planned to honour his achievements. As a small token of friendship and affection, the many friends of Kurt Bruck from all over the world who will participate in this event dedicate this symposium to the memory of Kurt Bruck. Another staunch friend, researcher of temperature regulation and supporter of this series of symposia died in October 1993: Professor Wilhelm Siegmund Feldberg. We feel fortunate to be able to start this volume with two brief infonnal and personal accounts of professors Bruck and Feldberg."

The concept for Vasopressin: Principles and Properties originated during the sum mer of 1983. From reviewing the rich and diverse literature on vasopressin, it became evident that the rapid advancements in this field made it difficult to syn thesize the information gathered from divergent scientific disciplines into a coherent view of the biological role of vasopressin. We perceived the need for a series of critical reviews delineating this recent progress. Over the past decade, major advances have been made in studies of the anatomy, physiology, phar macology, molecular biology, and behavioral activities of vasopressin. This is, in no small measure, due to the finding that vasopressin can no longer be regarded solely as a neurohypophysial hormone. Our present knowledge is that vasopressin is synthesized in also has an axonal messenger role in the nervous system and of the brain, although the functions of vasopressin in these periph sites outside of vasopressin eral sites are not well understood. In order to prepare an overview concentrating on recent studies in vertebrates, authors were selected based on their expertise and asked to review their research area, including the work from other laboratories. It was our intent to provide an updated definitive reference which would complement and extend such past texts as Neurohypophysial Hor mones and Similar Polypeptides (Handbook of Experimental Pharmacology, Vol ume XXIII, 1968) and The Pituitary Gland and Its Neuroendocrine Control (Handbook of Physiology, Section 7: Volume IV, 1974)."

Outlining the core principles of the subject, this introductory-level textbook covers the production of meat, its structure and chemical composition, meat quality and hygiene, and animal welfare, handling and slaughter. The new edition has been updated to cover significant advances such as the process of conditioning, leading to the tenderization of meat, and new coverage of the use of molecular genetic techniques to try to select animals for improved meat quality. It is an essential text for students and professionals in food science and technology, those working in the meat industry, meat inspectors, and vets.* New larger format in two colors throughout* Fully revised and updated including new coverage of genomics* Carefully selected references and titles for further reading

This book provides a comprehensive, up-to-date review of the distribution, pharmacology and physiology of central 5-hydroxytryptamine (5-HT)4 receptors. The 5-HT receptor subtypes exhibit a unique pharmacology, distribution and function, of which the 5-HT4 receptor has been one of the most intensively studied in recent years, both from a basic research standpoint and as a target for novel therapeutics.

Twenty five years ago, Bill Stebbins presented the principles of animal psychophysics in an edited volume (Stebbins, 1970) describing an array of modem, creative methodologies for investigating the range of sensory systems in a variety of vertebrate species. These principles included precise stimulus control, a well defined behavioral response, and a rigorous behavioral procedure appropriate to the organism under study. As a generation of comparative sensory scientists applied these principles, our knowledge of sensory and perceptual function in a wide range of animal species has grown dramatically, especially in the field of hearing. Comparative psychoacoustics, i. e. , the study of the hearing capabilities in animals using behavioral methods, is an area of animal psychophysics that has seen remarkable advances in methodology over the past 25 years. Acoustic stimuli are now routinely generated using digital methods providing the researcher with unprecedented possibilities for stimulus control and experimental design. The strategies and paradigms for data collection and analysis are becoming more refined as well, again due in large part to the widespread use of computers. In this volume, the reader will find a modem array of strategies designed to measure detection and discrimination of both simple and complex acoustic stimuli as well experimental designs to assess how organisms perceive, identify and classify acoustic stimuli. Refinements in modem methodologies now make it possible to compare diverse species tested under similar, if not identical, experimental conditions.

`Are the Great Lakes getting better or worse?' This is the question that the public, scientists and managers are asking the International Joint Commission after a quarter-century of cooperative action by the United States and Canadian governments to clean up the Great Lakes. This volume contains papers from the workshop on Environmental Results, hosted in Windsor, Ontario, by the Great Lakes Science Advisory Board of the International Joint Commission, on September 12 and 13, 1996. The Great Lakes have been through almost a century of severe pollution from the manufacture, use and disposal of chemicals. In the 1960s wildlife biologists started to investigate the outbreaks of reproductive failure in fish-eating birds and ranch mink and to link these to exposure to organochlorine compounds. Human health researchers in the 1980s and 1990s linked growth retardation, behavioral anomalies and deficits in cognitive development with maternal consumption of Great Lakes fish prior to pregnancy. The Great Lakes became the laboratory where the theory of endocrine disruptors was first formulated. Now a group of Great Lakes scientists, hosted by the International Joint Commission, has compiled the story of the trends in the concentrations and effects of persistent toxic substances on wildlife and humans. The technical papers review the suitability of various organisms as indicators, and present the results of long-term monitoring of the concentrations and of the incidence of effects. The evidence shows that there was an enormous improvement in the late 1970s, but that in the late 1990s there are still concentrations of some persistent toxic substances that have stubbornly remained at levels that continue to cause toxicological effects.

This book will give an overview of insect ovaries, showing the diversities and the common traits in egg growth processes. The idea to write this book developed while looking at the flood of information which appeared in the early 1980s on early pattern formation in Drosophila embryos. At this time a significant breakthrough was made in studies of this little fly, combining molecular biological methods with classical and molecular genetics. The answers to questions about early pattern formation raised new questions about the architecture of ovaries and the growth of eggs within these ovaries. However, by concentrating only on Drosophila it is not possible to form an adequate picture of what is going on in insect ovaries, since the enormous diversity found among insects is not considered sufficiently. Almost forgotten, but the first to study the architecture of ovaries, was Alexander Brandt writing in 1878 in aber das Ei und seine Bildungsstaette (On the egg and its organ of development). More than 100 years later, a series of ten books or more would be required to survey all the serious informa tion we have today on insect oogenesis. Thus, this book is a personal selection and personal view on the theme, and the authors must be excused by all those scientists whose papers could not be included. The book briefly describes the ectodemes, i. e."

Current Ornithology publishes authoritative, up-to-date, scholarly reviews of topics selected from the full range of current research in avian biology. Topics cover the spectrum from the molecular level of organization to population biology and community ecology. The series seeks especially to review (1) fields in which an abundant recent literature will benefit from synthesis and organization, or (2) newly emerging fields that are gaining recognition as the result of recent discoveries or shifts in perspective, or (3) fields in which students of vertebrates may benefit from comparisons of birds with other classes. All chapters are invited, and authors are chosen for their leadership in the subjects under review.

The basal forebrain has received considerable attention in recent years. This emphasis resulted from observations that the cortically projecting cholinergic neurons found in this region are critical for normal information processing. However, to achieve a complete understanding of such a complex function as "information processing" it is necessary to consider the basal forebrain not as an autonomous structure with a solitary task, but one that plays an integrative role; a structure that is connected intimately with many brain regions. This view evolved from the realization that the basal forebrain interfaces cognitive and reward functions with motor outputs. It is from this integrative and functional perspective that the present book was organized. The book is a unique collection of reports pertaining to the basal forebrain that encompasses a diversity of research approaches and techniques. It provides the reader with a progression of information that begins with anatomical descriptions of the afferent and efferent systems, stressing the integrative nature of various neurotransmitters located within the basal forebrain. The chapters focusing on anatomy are complemented by electrophysiologic studies that merge anatomical concepts with synaptic pharmacology and behavior. In vitro experiments demonstrate physiologic variations in anatomically identified neuronal subtypes and, together with in vivo techniques, provide pharmacologic descriptions of neuronal consequences to various neurotransmitter influences. Additional in vivo reports correlate changes in neuronal activity with specific motivational states and motor behaviors. These functional approaches culminate with behavioral studies that overview current understanding of basal forebrain involvement in mnemonic, reward, and motor processes.

Muscle contraction has been the focus of scientific investigation for more than two centuries, and major discoveries have changed the field over the years. Early in the twentieth century, Fenn (1924, 1923) showed that the total energy liberated during a contraction (heat + work) was increased when the muscle was allowed to shorten and perform work. The result implied that chemical reactions during contractions were load-dependent. The observation underlying the "Fenn effect" was taken to a greater extent when Hill (1938) published a pivotal study showing in details the relation between heat production and the amount of muscle shortening, providing investigators with the force-velocity relation for skeletal muscles. Subsequently, two papers paved the way for the current paradigm in the field of muscle contraction. Huxley and Niedergerke (1954), and Huxley and Hanson (1954) showed that the width of the A-bands did not change during muscle stretch or activation. Contraction, previously believed to be caused by shortening of muscle filaments, was associated with sliding of the thick and thin filaments. These studies were followed by the classic paper by Huxley (1957), in which he conceptualized for the first time the cross-bridge theory; filament sliding was driven by the cyclical interactions of myosin heads (cross-bridges) with actin. The original cross-bridge theory has been revised over the years but the basic features have remained mostly intact. It now influences studies performed with molecular motors responsible for tasks as diverse as muscle contraction, cell division and vesicle transport.

by G. MILAZZO and M. BLANK This book contains the lectures of the fourth advanced course Bioelectrochemislry W Neroe-Muscle Function: Bioelectrochemistry, Mechanisms, Energetics and Contro~ which took place at the Majorana Center in Erice, Italy, October 20th to November 1, 1991. The scope of the course was international in terms of both sponsorship and partici pation. Sponsors included the Bioelectrochemical Society, NATO, International Union of Pure and Applied Biophysics (lUPAB), the World Federation of Scientists and the Italian National Research Council. One-third of the sixty participants were from Italy, but the majority came from eighteen other nations. Since the course was part of the International School of Biophysics, the biophysi cal point of view was emphasized in integrating the biology with the electrochemistry. Lecturers were asked to use a quantitative approach with accepted standards and proper units, since this is absolutely essential for developing an effective common language for communication across disciplines. Participants were also urged not to forget that biological systems could also be considered as physical systems. Ion channels are proteins and their properties as polyelectrolytes contribute to the specific biological properties. The existence of families of channels, with very similar structures but different selectivities, suggests that the specificities arise from slight variations of a general basic design. These perspectives on nerve-muscle function helped to make the school course a unique treatment of the subject.

Volumes I and 2 of this Plant Biotechnology series reviewed fundamental aspects of plant molecular biology and discussed production and analysis of the first generation of transgenic plants of potential use in agriculture and horticulture. These included plants resistant to insects, viruses and herbicides, which were produced by adding genes from other organisms. Realisation of the potential of plant breeding has led to a resurgence of interest in methods of altering the structure, composition and function of plant constituents, which represents an even greater challenge and offers scope for improving the quality of a wide range of agricultural products. This, in tum, has resulted in a re-evaluation of priorities and targets by industry. Volume 3 of this series considers the biochemical and gentic basis of the biosynthesis of plant products such as starch, lipids, carotenoids and cell walls, and evaluates the ways in which biosynthesis of these products can be modified for use in the food industries. Authors also cover the biosynthesis of rare secondary products and the function and application of proteins for plant protection and therapeutic use. The emphasis throughout is on the relationship between fundamen tal aspects of biosynthesis and structure-function relationships, and application of this knowledge to the redesigning and altering of plant products by molecular genetics."

Fish comprise more than 50% of all living vertebrates and are found in a wide range of highly diverse habitats like the deep sea, the shoreline, tide pools, tropical streams and sweetwater ponds. During evolution, the senses of fish have adapted to the physical conditions of the environment in which different species live. As a result, the senses of fish exhibit a remarkable diversity that allows different species to deal with the physical constraints imposed by their habitat. In addition, fish have evolved several new' sensory systems that are unique to the aquatic environment.
In this book, examples of adaptation and refinement are given for six sensory systems: The visual system, The auditory system, The olfactory system, The mechanosensory lateral line system, The taste system, The electrosensory system. In each case, the environmental conditions under which a particular group of fish lives are analyzed. This is followed by a description of morphology and physiology of the sensory system and by an evaluation of its perceptional capabilities. Finally, the sensory adaptations to the particular conditions that prevail in the habitat of a species are highlighted.
The various examples from different groups of fish presented in this book demonstrate the impressive capability of fish sensory systems to effectively overcome physical problems imposed by the environment.

From within complex structures of organisms and cells down to the molecular level, biological processes all involve movement. Muscular fibers slide on each other to activate the muscle, as polymerases do along nucleic acids for replicating and transcribing the genetic material. Cells move and organize themselves into organs by recognizing each other through macromolecular surface-specific interactions. These recognition processes involve the mu tual adaptation of structures that rely on their flexibility. All sorts of conformational changes occur in proteins involved in through-membrane signal transmission, showing another aspect of the flexibility of these macromolecules. The movement and flexibility are inscribed in the polymeric nature of essential biological macromolecules such as proteins and nucleic acids. For instance, the well-defined structures formed by the long protein chain are held together by weak noncovalent interac tions that design a complex potential well in which the protein floats, permanently fluctuating between several micro- or macroconformations in a wide range of frequencies and ampli tudes. The inherent mobility of biomolecular edifices may be crucial to the adaptation of their structures to particular functions. Progress in methods for investigating macromolecular structures and dynamics make this hypothesis not only attractive but more and more testable.

Research on thrombin structure and function has progressed significantly over the past three decades. We are continually discovering new functions f()r this enzyme in biology. Yet, until quite recently, a full, detailed, three dimensional picture of its structure was difficult to attain. We believe that this text represents a turning point and, more appropriately, a new start ing point for thrombin studies. Our goal for this text is to present a thorough and rounded-out coverage of thrombin chemistry and biochem istry in order to provide the biochemist and physiologist with an excellent desk reference on almost any thrombin-related problem. This volume is organized into three general thrombin topic areas: Structure, Biochemistry, and Physiology. In Part 1, Structure, we open with the complete three-dimensional x-ray structures of two inhibited human thrombin complexes, one of which is the thrombin-hirudin com plex. These complexes are also addressed in the chapter on structural studies in solution, which include NMR, ESR, and fluorescence. Part 2, Biochemistry, includes chapters on synthetic thrombin inhibitors, protein inhibitors (e.g., antithrombin III, hirudin), and thrombin interactions with factor XIII. Part 3, Physiology, covers such topics as chemotactic activities, interactions with cell surfaces, and the vascular endothelium.

Mesodenn is a key tissue in early development. It is involved in the differentiation of almost every organ in the body, not merely as a structural component, but as an active participant in the establishment of diverse cell types. All mesodenn is derived from ectoderm. Its appearance signals the start of a significant new phase in the development of the embryo. At this time all three genn layers are now present and myriad sequences of cell and tissue interactions begin to occur which will eventually give rise to the entire embryo. The control of the growth and differentiation of the mesoderm is critical for the production of a normal individual. Indeed, disturbance of the patterning of the mesoderm or of its interaction with other tissues plays a critical part in the fonnation of most congenital anomalies. The main focus of this book is therefore on the establishment, divergence and specialisation of mesodermal derivatives. The central role of the mesoderm in development has long been appreciated and a wide literature exists on its activity in certain specialised situations. Recently, however, an impetus to its study has been provided by new approaches opened up through biotechnological advances. Many of these advances are reflected in the reports in this volume. Scientists from various disciplines have become drawn to mesodermal tissues, and this volume may help them find a framework within which their work will fit.

In March 1996 the Society of Experimental Biology (UK) together with two other international scientific societies, the Australian and New Zealand Society for Comparative Physiology and Biochemistry and the Society for Integrative and Comparative Biology (formally the American Society for Zoology) joined forces with Springer-Verlag, Heidelberg to produce one of the first fully electronic online, peer-reviewed biological journals, Experimental Biology Online. The present product represents the fruits of this joint venture and encapsulates Volumes 1 and 2 of the journal. This will be an ongoing series such that an archival version of the journal will be available to all libraries as well as the on-line version. At the outset this was "new land" for all concerned but the launching of a journal which would cover experimental biology in terms of Animal, Cell and Plant topics was daunting but we all felt that the use of electronic media and the internet would be ideally suited to this purpose.

One of the most impressive advances in the field of neuroscience over the last decade has been the accumulation of data on plasticity and regeneration in the nervous system of mammals. The book represents the contribution of a qroup of neuroscientists to this rapidly expanding field, through a Conference organized by the Institute of Developmental Neuroscience and Aging (IDNA). The meeting was held in Torino, Italy during April 1990 in honor of a great pioneer in the field of Neuroembryology, Professor Guido Filogamo. His introduction of the concept of neuroplasticity has had a significant impact on the study of neurobiology. This volume is divided into six sections, each focusing on one of the subject areas covered during the meeting Molecular and Cellular Aspects of Central and Peripheral Nervous System Development; Hormones,* Growth Factors, Heurotransmi tters, Xenobiotics and Development; In Vivo and in Vitro models of Development; Development and Regulation of Glia; Regeneration; and Aging.

In recent years rapid progress has been made in the areas of T cell and B cell biology, cell-cell and cell-matrix/stroma interactions. The use of isolated subunits of the T cell receptor invariant chains has been instrumental in defining their role in signal transduction and tyrosine phosphorylation. A role of src family phosphotyrosine kinases in T cell activation has been demonstrated and several phosphotyrosine kinase substrates have been identified and their functions characterized. Homologous recombinant techniques have led to the development of murine strains that lack CD4 or CD8 expression. These models are likely to be instrumental in studying the role of T cell subsets in autoimmune disorders, tissue transplant rejection and tumor rejection. A role of major histocompatibility complex I in the development of T cell subsets and NK cells has been defined. Recent data suggest a role of interaction between plasma membrane molecules of activated T helper cells and B cells, B cells primed with plasma membrane of activated T helper cells and cytokines, and interaction between bone marrow stromal cells and B cell progenitors and precursors, in the B cell development, proliferation, and differentiation. The structure and functions of adhesion molecules, especially with regard to signal transduction and homing events, are better defined.

This volume represents the proceedings of the 9th International Proton Transport Conference, "Mechanisms and Consequences of Proton Transport" held in Leura, Australia, August 19 -21, 200 I. This conference has been held since 1971 every 3 to 4 years with few exceptions in association with the Congress of the International Union of Physiological Sciences. The first meeting was held in Frankfurt, Germany, at the Max-Planck'Institute. Countries hosting the conference have been Germany (twice), Sweden (twice), India, Canada, USA, Great Britain, and now Australia. Over the past 30 years participants at these Proton Transport Conferences have been principal contributors to the major discoveries in the physiology, biochemistry and pharmacology of gastric acid secretion. These include development of the H2-receptor blockers, defining the signaling pathways for the regulation of acid secretion, identifying the gastric proton pump, discovery and development of proton pump inhibitory drugs, and elucidating the physiology and biochemistry of Helicobacter pylori.

The Henry Goldberg Workshops were set up to address the following goals: (1) To foster interdisciplinary interaction between scientists and cardiologists, identify missing links, and catalyze new ideas. (2) To relate basic microscale phenomena to the global, clinically manifested cardiac function. (3) To relate conceptual modeling and quantitative analysis to experimental and clinical data. (4) To encourage international cooperation so as to disperse medical and technological knowhow and lead to better understanding of the cardiac system. The first Henry Goldberg Workshop, held in Haifa in 1984, introduced the concept of interaction between cardiac mechanics, electrical activation, perfusion, and metabolism, emphasizing imaging in the clinical environment. The second Workshop, in 1985, discussed the same parameters with a slant towards the control aspects. The third Goldberg Workshop, held in the USA at Rutgers University in 1986, highlighted the transformation of the microscale activation phenomena to macroscale activity and performance, relating electrophysiology, energy metabolism, and cardiac mechanics. The fourth Goldberg Workshop, in 1987, continued the effort to elucidate the interactions among the various parameters affecting cardiac performance, with emphasis on the ischemic heart. The fifth Workshop, held in Cambridge, UK, in 1988, dwelt on the effects of inhomogeneity of the cardiac muscle on its performance in health and disease. The sixth Workshop highlighted the role of new modem imaging techniques, that allow us to gain more insight into local and global cardiac performance in cardiac research and clinical practice.

Serpins (serine protease inhibitors) are a superfamily of proteins whose physiologi- cal action is primarily targeted to inhibiting serine proteases. There are instances where serpins are not inhibitors (and can carry steroid hormones for instance), yet key structural and functional elements found in all serpins are maintained in these 'non-inhibitor' ser- pins. Many serpins have well-described biological properties which influence pathophysi- ological events, including: antithrombin (historically called antithrombin III), ai-protease inhibitor (historically called ai-antitrypsin), and plasminogen activator inhibitor-I, just to mention a few. A deficiency or defect in antithrombin leads to venous thromboembolic disease, while a deficiency or defect in ai-protease inhibitor is associated with chronic obstructive pulmonary emphysema. In contrast, it has been suggested that increased levels of plasminogen activator inhibitor-l may be a predisposition to myocardial infarction. The list goes on for each of our own "favorite" serpin. The biological roles found for serpins are key participants in almost every physiological event. In other words, serine proteases are needed for many events in biology and the role of serpins to down regulate these pro- teases is essential. Thus, just using these three examples above for serpins and their patho- physiological roles reminds us that the medical costs to control such events is significant worldwide.

This monograph contains the proceedings from the Advanced Study Institute on "Vascular Endothelium: Physiological Basis of Clinical Problems" which took place in Corfu, Greece in June 1990. The meeting consisted of twenty-eight lectures, most of them adapted as full length papers in this volume, as well as numerous short oral and poster communications which are abstracted and also included in alphabetical order (pages 239-302). There were ninety-six participants from ten NATO and four other European countries. The meeting was the second in as many years dealing with a specific subject in Endothelial Cell biology. Following the 1988 discussion on "Receptors and Transduction Mechanisms", the present ASI recognized and tried to deal with the increasing overlap in interest between basic scientists studying endothelial cell functions and clinicians facing problems of known or suspected endothelial pathological involvement. As with any similar effort, we opted to be selective, rather than fail by trying to be inclusive, in the subjects covered. We chose to discuss diseases, such as atherosclerosis, sepsis, ARDS and stroke, based on their relevance to endothelial cell function and urgent need for new insights into their pathogenesis and treatment. Similarly, we examined endothelial cell functions by considering their relevance to disease and their potential for elucidating important pathologies. Obviously, some areas were covered superficially or not at all; this should not distract from their importance, but rather reflect on the constraints of time and -not at all negligibly -the bias of the organizing committee.

During the past decade interest in the formation of complex disorderly patterns far from equilibrium has grown rapidly. This interest has been stim ulated by the development of new approaches (based primarily on fractal geometry) to the quantitative description of complex structures, increased understanding of non-linear phenomena and the introduction of a variety of models (such as the diffusion-limited aggregation model) that provide paradigms for non-equilibrium growth phenomena. Advances in computer technology have played a crucial role in both the experimental and theoret ical aspects of this enterprise. Substantial progress has been made towards the development of comprehensive understanding of non-equilibrium growth phenomena but most of our current understanding is based on simple com puter models. Pattern formation processes are important in almost all areas of science and technology, and, clearly, pattern growth pervades biology. Very often remarkably similar patterns are found in quite diverse systems. In some case (dielectric breakdown, electrodeposition, fluid-fluid displacement in porous media, dissolution patterns and random dendritic growth for example) the underlying causes of this similarity is quite well understood. In other cases (vascular trees, nerve cells and river networks for example) we do not yet know if a fundamental relationship exists between the mechanisms leading the formation of these structures.