The purpose of this volume is to review and discuss key growth factor systems that have been implicated in embryogenesis. Emphasis is placed on the insulin family of peptides, including insulin and the structurally and functionally related insulin-like growth factors. The initial chapters provide a review of basic topics, including developmental genetics, energy metabolism and hormonal signaling mechanisms, which are important prerequisites to the central theme that follows. The book concludes with a brief review of oncogene expression in early development; this new field has contributed significantly to our understanding of how mitogenic signals activate genetic elements responsible for embryonic growth and development. This book presents information important to cell biologists, endocrinologists, biological chemists, and developmental biologists.