His laboratory developed a widely used confocal micro-angiography method, compiled an atlas of the anatomy of the developing zebrafish vasculature, developed numerous vascular-specific transgenic fish lines, and pioneered methods for high resolution in vivo imaging of zebrafish blood vessels. His laboratory has used all of these tools and methods to make a variety of important discoveries in the areas of vascular specification, differentiation, and patterning, including a novel pathway specifying arterial identity, a role for neuronal guidance factors in vascular patterning, a mechanism for vascular tube formation in vivo, and the identification of a lymphatic vascular system in the zebrafish.