The book summarizes our progress in understanding the receptor and intracellular signaling mechanisms utilized by a family of proteins called the semaphorins. Originally these protein were identified as 'axon guidance cues' important for the formation of nerve tracts but now it is realized that semaphorins subserve several distinct functions in a multitude of organ systems. The purpose of this book is to summarize our knowledge and make it available as a useful and comprehensive tool for the scientific community. This book will both be interesting for people working in the field as well as colleagues that work in other fields of science and would like to learn more about semaphorins and associated signaling mechanisms. All the latest techniques and results are summarized in this book which covers the entire semaphorin field from neurosciences to cardiovascular research and beyond. The strength of this book is that it gives a very comprehensive overview of all our knowledge of semaphorin biology and signaling and allows one to compare semaphorin functions between different biological systems.