The sex organs of animals are some of evolution’s most diverse handiwork. And yet up until now, scientists haven’t understood exactly how they evolved and take shape at the earliest stages of development. In a recent study, researchers have begun to unravel how genitals form. Patrick Tschopp, research fellow in genetics, is first author of the research. Clifford Tabin, George Jacob and Jacqueline Hazel Leder Professor of Genetics and head of the Department of Genetics, is senior author.