Angiogenesis, or the sprouting of blood vessels from pre-existing ones is a key process in shaping the vasculature. So far, angiogenesis research has mainly focused on identifying genetic players. My proposed research takes a completely novel approach towards understanding angiogenesis by addressing the question how physiological factors, such as changes in blood flow dynamics, influence endothelial biology. I will furthermore address the question if there is an interaction between genetic and physiological influences during angiogenesis. My proposed research will tackle these outstanding questions in endothelial biology using several cutting edge technologies. First, I will perform long term time lapse imaging of the growing vasculature using 2-Photon microscopy. Second, I will use an innovative methodology employing zinc finger nuclease mediated gene targeting to rapidly generate mutant zebrafish in genes implicated in mediating the effects of hemodynamics on angiogenesis. Third, I will laser ablate individual blood vessels in living zebrafish embryos to alter blood flow patterns and study the influence of those changes on angiogenesis. These challenging technological advancements will make it possible for the first time to understand how physiological factors aid in shaping the forming vascular system. These findings will have broad applicability to angiogenic processes in many different vascular beds and developmental time points. Importantly, the mechanisms at play during vascular development in the embryo are reactivated in the adult in situations of pathological angiogenesis, such as tumor progression or ischemia. Therefore, applying this knowledge to angiogenesis occuring in pathological settings will provide us with new avenues for improved disease treatments.