This volume documents the progress made in the design of complex artificial systems and in the study of intermolecular forces and interactions. It is possible, using appropriate strategies based on building blocks, to obtain very large supramolecular arrays containing several hundered atoms, where specific sites are occupied by the desired chemical functions. Such arrays can be used for such things as molecular recognition, self-organization, self-replication, selective reactivity, selective catalysis, photoinduced energy and electron transfer, signal processing, information storage and drug delivery.

The intellectual and utilitarian opportunities that lie at the frontiers of chemistry have been recently emphasized by the Pimentel Report. Such report recommends that in the field of chemical research priority should be given to "understanding chemical reactivity" and proposes initiatives aimed at the clarification of factors that control the rates of reaction and the development of new synthetic pathways for chemical change. In the broad field of chemical reactivity, a discipline that has grown with an extraordinary rate is photochemistry. Since the knowledge of the photochemical properties at the molecular level has made a substantial progress in the last few years, there is currently a trend to study more and more complex photochemical systems. In particular, an emerging and rapidly expanding branch of photochemistry is that concerning studies of assemblies of molecular components properly combined so as to obtain light-induced functions (supramolecular photochemistry). Although much of the current work in supramolecular photochemistry is fundamental in nature, it is clear that progress in this field will be most rewarding for several applications concerning the interaction of light with matter. In particular, it will allow us to pursue research aimed at the photochemical conversion of solar energy by means of artificial systems and to make progress towards futuristic branches of science called "photonics" (photo-generated electron migration processes on a molecular basis) and "chemionics" (design of components, circuitry, and information treatment at the molecular level).

Photochemistry (a term that broadly speaking includes photophysics) is abranchofmodernsciencethatdealswiththeinteractionoflightwithmatter and lies at the crossroadsof chemistry, physics, and biology. However, before being a branch of modern science, photochemistry was (and still is today), an extremely important natural phenomenon. When God said: "Let there be light", photochemistry began to operate, helping God to create the world as wenowknowit.Itislikelythatphotochemistrywasthesparkfortheoriginof life on Earth and played a fundamental role in the evolution of life. Through the photosynthetic process that takes place in green plants, photochemistry is responsible for the maintenance of all living organisms. In the geological past photochemistry caused the accumulation of the deposits of coal, oil, and naturalgasthat wenowuseasfuels.Photochemistryisinvolved inthecontrol ofozoneinthestratosphereandinagreatnumber ofenvironmentalprocesses thatoccurintheatmosphere,inthesea,andonthesoil.Photochemistryisthe essenceoftheprocessofvisionandcausesavarietyofbehavioralresponsesin living organisms. Photochemistry as a science is quite young; we only need to go back less than one century to ?nd its early pioneer [1]. The concept of coordination compound is also relatively young; it was established in 1892, when Alfred Werner conceived his theory of metal complexes [2]. Since then, the terms coordination compound and metal complex have been used as synonyms, even if in the last 30 years, coordination chemistry has extended its scope to the binding ofall kinds of substrates [3, 4].

This book presents critical reviews of the current position and future trends in modern chemical research. It offers short and concise reports on chemistry, each written by world renowned experts.

The first NATO Science Forum was held in Biarritz in September 1990. This Taormina Conference is the second in a series that we wish to be a long one and I believe that it has equalled the success of its predecessor. In setting up these meetings the NATO Science Committee wanted to gather leading experts to review fields of strong present interest. It was intended that presentations and discussions should pay special attention to potential developments. This "forward look" is indeed precious to us in mapping out the evolution of our Science Programme but more importantly, it is an essential part of the progress of Science. I believe that NATO, being able to bring together eminent scientists from both sides of the Atlantic, is in a priviliged position to provide this service to our Scientific Community. It was only proper that Chemistry should be one of the first areas to be targeted: a central science with many rich borders touching on other disciplines, it deserved the full attention of our Committee. In its vast domain, among many possible topics, the present one was carefully selected and its choice resulted from an extensive consultation of many leading chemists. The large fraction of replies which pointed to Supramolecular Chemistry left us with little doubt about the timeliness of a Forum in this area and the strong interest attached to it.

The intellectual and utilitarian opportunities that lie at the frontiers of chemistry have been recently emphasized by the Pimentel Report. Such report recommends that in the field of chemical research priority should be given to "understanding chemical reactivity" and proposes initiatives aimed at the clarification of factors that control the rates of reaction and the development of new synthetic pathways for chemical change. In the broad field of chemical reactivity, a discipline that has grown with an extraordinary rate is photochemistry. Since the knowledge of the photochemical properties at the molecular level has made a substantial progress in the last few years, there is currently a trend to study more and more complex photochemical systems. In particular, an emerging and rapidly expanding branch of photochemistry is that concerning studies of assemblies of molecular components properly combined so as to obtain light-induced functions (supramolecular photochemistry). Although much of the current work in supramolecular photochemistry is fundamental in nature, it is clear that progress in this field will be most rewarding for several applications concerning the interaction of light with matter. In particular, it will allow us to pursue research aimed at the photochemical conversion of solar energy by means of artificial systems and to make progress towards futuristic branches of science called "photonics" (photo-generated electron migration processes on a molecular basis) and "chemionics" (design of components, circuitry, and information treatment at the molecular level).

Many people are convinced that, among other courses taught in schools, chemistry is a difficult and complex subject. This view is often arrived at without justification. Setting out to introduce chemistry concepts and demystify chemistry, this book shows how it is a major part of our everyday lives. It introduces the readers into the wonderful world of atoms and molecules and chemical reactions whilst showing that chemistry is centrally important but also an emerging science and defines what the practising chemist does. The book also examines curiosity, creativity, fascination, poetry, beauty, and ethics in science. Originally published in Italian, 'Chimica - leggere e scrivere il libro della Natura' was among the finalists of the 2013 Italian Award for popularization of science. The English translation has been sensitively delivered to explain concepts in simple language and emphasize the positive role that chemistry can play to shape our future.