The growth of pancreatic endocrine cells occurs early in the developing embryo. The signals that initiate the development are not defined, but several secreted proteins participate directly or indirectly in the differentiation of epithelial cells into hormone-producing cells. A recent study now suggests that vascular endothelial cells produce factors that are crucial for the induction of pancreatic organogenesis and for the formation of insulin-producing cells. The identification of these factors could be key to the efficient generation of insulin-producing cells from embryonic stem cells or other proliferating pancreatic precursor cells.