Multicellular organisms coordinate proliferation with other developmental processes to establish patterns, to achieve specific organ size, and to reach final organism size and to maintain organ homeostasis. This coordination requires that individual cells correctly interpret intrinsic and extrinsic cues and respond appropriately with the decision to grow, proliferate, differentiate, or die. My research program explores these fundamental processes with a focus on how growth and proliferation are regulated and how loss of that regulation leads to disease. We employ the synergistic systems of in vivo Drosophila (fruit fly) genetics, tissue culture, and in vitro biochemistry to investigate (1) Ras signaling, (2) the Hippo Tumor Suppressor Pathway, and (3) to develop fly models of human disease.