Matt Scott investigates how genes gave rise to new body plans. His model is the fruit fly and the genes that control how the body is built. Geneticists, like Scott, often look at mutations to find their answers. Scott shows us a mutant fly. Mutant flies led to the discovery of Hox genes, regulatory genes that tell an embryo how to build the basic form of an animal. Scott is excited about the realization that similar genes build similar structures in very different animals.