Few of us know much about the biology of sex determination, but what could be more interesting than to discover how we are shaped into males and females? In this book, Elof Carlson tells the incredible story of the difficult quest to understand how the body forms girls and boys. Carlson's history takes us from antiquity to the present day to detail how each component of human reproduction and sexuality was identified and studied, how this knowledge enlarged our understanding of sex determination, and how it was employed to interpret such little understood aspects of human biology as the origin of intersex births.