The development of organs of species-specific size and shape is a process of extreme robustness. This is striking, taking into account the numbers of cell interacting during the process, and the myriad of noisy biochemical reactions operating within each of them. In order to gain insight into how development controls organogenesis, in our lab we have reduced this problem to understand the progenitor-to-precursor cell transition during the development of the Drosophila eye. By regulating the number of proliferative progenitors and the pace at which they are forced out of the cell cycle and recruited as quiescent precursors, the developing eye may control its size. In our lab we use genetic, transgenesis, genomics and mathematical modeling to understand the gene regulatory network (GRN) that governs this progenitor-to-precursor transition, and how this network is dynamically controlled to consistently yield eyes of the “correct” size and shape. In addition, by using comparative approaches, we aim at defining the essential elements and regulatory operations of a “minimal” visual GRN. The model organism is Drosophila in which, in addition to the cohort of tools available, there is extensive knowledge of the genes and signaling pathways involved in the early control of eye development. See the Specific Projects page for a more complete description of our work.