We are taking innovative approaches to study morphogenesis within a developing organism and to leverage that understanding to develop tools and blueprints for building tissues of defined shape and structure in the lab. We propose to develop approaches to control cell-generated mechanical forces within tissues to dissect how patterns of forces control the fundamental cell behaviors that transform simple epithelial tissue sheets into complex tissue architectures in the Drosophila embryo. To do this, we are combining emerging optogenetic approaches for light-gated control of proteins to control actomyosin force generation, live in vivo confocal imaging, and biophysical approaches to study tissue mechanics and morphogenesis. This work will make force an experimentally tunable parameter in vivo, provide a foundation for integrating mechanics into our understanding of how genetic factors control morphogenesis, and motivate new strategies for building functional tissues in vivo and in vitro.