"Understanding the transition from molecular to cellular patterns and then to elaborate biological forms remains a major challenge in developmental biology. Recent advances in biological imaging enable to study the complex mechanisms that control tissue and organ morphogenesis. I will focus on animal appendages that develop particular shapes and sizes to suit the lifestyle of the organisms. Among animal models, the crustacean Parhyale hawaiensis offers a unique capacity for microscopic live imaging and tracking of all cells of developing appendages continuously from early specification up to late differentiation. Parhyale embryos undergo direct development from fertilized eggs into miniature adults, they are transparent and amenable to all sorts of embryological and functional genetic manipulations. Importantly, each Parhyale embryo develops a variety of specialized appendages along the anterior-posterior body axis that differ in size, shape and pattern. I will study how morphogenetic mechanisms are deployed differentially in these neighboring growing appendages to produce their morphological differences. Transgenic embryos expressing fluorescent tracers will be recorded with Selective Plane Illumination Microscopy in vivo throughout appendage development. Using these time-lapse recordings, I will first generate and compare the cell lineages of serially homologous appendages to identify patterns that account for their morphological differences. I will then quantify the cell behaviors that contribute to appendage growth and form, including rates and patterns of cell division and cell death and orientation of cell divisions. Finally, I will investigate at single-cell resolution how the Hox regulatory genes guide distinct cell behaviors to control appendage morphogenesis. This line of research will elucidate how dynamic patterns of gene activity control dynamic cell behaviors during development to generate the diversity of appendage and organ forms observed in nature."