Development after embryogenesis requires exquisite control of signaling between individual tissues to build an adult organism of the proper shape and size. This intercellular communication is directed by groups of specialized secretory cells that release systemic signals; these signals then orchestrate biological responses in target tissues. Once a tissue has received a signal, it can respond by growing, remodeling, or dying. Thus, the interplay between secretion of systemic signals and response in receiving tissues is essential to unfold the genetically-encoded developmental program of multicellular organisms. One of the most dramatic examples of this interplay between signals and responses occurs during insect metamorphosis, the developmental stage that transforms a crawling larva into a flying adult. In the Bashirullah Lab, we combine forward genetic approaches with cellular and molecular biology to uncover novel essential genes and new biological processes that regulate the onset of and progression through Drosophilametamorphosis. We have discovered important new roles for endocrine and exocrine biology during metamorphosis that have important implications for human development and disease.