The formation of blood vessels is an essential aspect of embryogenesis in vertebrates. It is a central feature of numerous post-embryonic processes, including tissue and organ growth and regeneration. It is also part of the pathology of tumour formation and certain inflammatory conditions. In recent years, comprehension of the molecular genetics of blood vessel formation has progressed enormously and studies in vertebrate model systems, especially the mouse and the zebrafish, have identified a common set of molecules and processes that are conserved throughout vertebrate embryogenesis while,