Perhaps the most remarkable recent discovery in developmental biology is that the molecular mechanisms that pattern the animal embryo have been conserved throughout evolution. Many of the genes that specify embryonic pattern were first identified in the fruitflyDrosophila melanogasterand later studied in vertebrates. In this chapter, I focus on the anterior region of the fly embryo, which includes the head and brain. I describe the morphological and molecular tools that have been used to identify and analyze the genes that specify the head and brain.
