The process whereby a single cell, the fertilized egg, develops into an adult has fascinated for centuries. Great progress in understanding that process, h- ever, has been made in the last two decades, when the techniques of molecular biology have become available to developmental biologists. By applying these techniques, the exact nature of many of the interactions responsible for forming the body pattern are now being revealed in detail. Such studies are a large, and it seems ever-expanding, part of most life-science groups. It is at newcomers to this field that this book is primarily...