During heart development, the coronary vasculature forms by establishment of an endothelial plexus that expands around the heart. Current evidence suggests that the sinus venosus (SV), endocardium and proepicardium may all contribute to coronary development. However, the relative contributions of these sources and the molecular mechanisms regulating coronary angiogenesis are still unclear. In a detailed lineage-tracing analysis in mouse (p. 4500), Kristy Red-Horse and colleagues find that the SV and endocardium make spatially restricted and complementary contributions to the coronary vasculature, with dorsal and lateral vessels having primarily SV origin, while the endocardium contributes significantly to vessels of the ventral heart and ventricular septum. The proepicardium makes a minor, but non-spatially restricted, contribution. VEGFA has previously been shown to promote angiogenesis of a subpopulation of coronary vasculature, and the authors now find that VEGFC promotes growth of a complementary set of vessels – those derived from the SV. These data provide a comprehensive view of the sources of the coronary endothelium and help to unravel the mechanisms by which these vessels form.