Platelet-derived growth factor-B (PDGFB) is necessary for microvasculature formation, and loss of PDGFB or its receptor – PDGF receptor β(PDGFRβ) – causes a wide range of abnormalities in mice, including defects of the heart, kidney and placenta. The formation of functional new vessels requires the recruitment of vascular-smooth muscle cells (VSMC) and pericytes, both of which express PDGFRβ and are thought to be primary targets for PDGFB. Bjarnegård and co-workers(p. 1847) have now determined the source of PDGFB involved in this process. PDGFB is produced from several cell types, including platelets and macrophages, but, using Cre-lox techniques, the researchers show that it is PDGFB from the endothelium that is crucial for pericyte recruitment. Furthermore, the phenotype of endothelium-restricted Pdgfb knockout mice resembles diabetic microangiopathy, prompting the authors to suggest that endothelium-restricted PDGFB mutants could provide a useful model for vascular complications of diabetes.