This volume reviews our current understanding for how sex determination is initiated and how it results in sexual dimorphic development. Chapters discussing work on different model systems provide a basis for understanding similarities that exist between different species. Coverage includes discussion of sexual development of the soma in C. elegans; sexual development of the germline in C. elegans; sexual development of the soma in Drosophila; sexual development of the germline in Drosophila; sexual development of the soma in the mouse; sexual development of the germline in the mouse; control of sex-specific behavior in Drosophila; and control of sex-specific behavior in vertebrates.This book uncovers the latest research findings on sexual determination and sexual development. Detailed model systems illustrate species differences and similarities. It thoroughly explains sexual development across various germlines including Drosophila. The book outlines the origins and control of sex-specific behavior.