In this volume of ASPA, devoted to developmental biology research, 9 authors from different fields of developmental biology present their investigations on various developing plant and animal models. An "a priori" concern in mind that weightlessness might have negative effects on developmental processes, it is encouraging to know that the overall development of various organisms tested so far is essentially correct under spaceflight conditions, leading to viable individuals with viable offspring. On the other hand, particular studies on specifically neurophysiological aspects in developing organisms reveal important flight or postflight disturbances; however it is encouraging to know that they appear to be transient only.
The book contains ten chapters, giving details on how, in technical terms, experiments for spaceflights are prepared, performed and analysed and on how, in scientific terms, the available results have to be interpreted. One contribution is devoted to plant systems, five consider the overall aspects of embryonic development in invertebrates and vertebrates, two focus on neurophysiological aspects and one reports on the "mother-offspring system" in weightlessness in a mammalian model, the last chapter presents new ESA facilities and instruments to be integrated into the European research Laboratory "Columbus" of the ISS.

The NATO Advanced Study Institute on "Cellular and Molecular Control of Direct Cell Interactions in Developing System" has been attended by 15 invited main lecturers and 60 participants. According to its purpose senior scientists, postdoctoral trainees and graduate students working in areas like biology, biochemistry, electrophysiology, medicine etc . . . could discuss their common interest in the various structural, ultrastructural, molecular and functional aspects of cell interactions in developing in vivo and in vitro systems. Whereas the topics of the first week have been mostly concerned with the general aspects of cell interactions in embryogenesis (section I and II of this book), the second week has been mainly devoted to the structures and functions of the direct cell contact sites at the membrane level as gap junctions, including electrophysiological aspects, dye coupling and selective cell-cooperation in some model systems as the neuro-muscular junctions (section III-V of this book). A multidisciplinary and stepwise approach, from initial cell contacts in early embryogenesis up to well defined selective cell cooperation, appeared to be an efficient means to provide answers to the question of how cells control, in a dynamic system as given in a differentiating embryo, their multiple temporary and permanent interactions so necessary for ordered cell positioning, cell linking and well established cell-to-cell communication.