e have resisted the temptation to cover every aspect of development and have, instead, focused on those systems that best illuminate common principles. Indeed a theme that runs throughout the book is that universal principles govern the process of development.' (Lewis Wolpert, Introduction) Principles of Development is designed for undergraduates. The emphasis is on principles and key concepts. Central to the authors' approach is that development can best be understood by understanding how genes control cell behaviour. They have assumed that students have some basic familiarity with cell biology and genetics, but all key concepts, like the control of gene activity, are explained in the text, and an extensive glossary is provided too. The authors have resisted the temptation to cover every aspect of development and have instead focused on those systems that best illuminate common principles. Indeed, a theme that runs throughout the book is that there are universal principles governing development. At all stages what they have included has been guided by what they believe undergraduates should know about development. The focus of the text is on vertebrates and Drosophila, but not to