The eye contains highly vascularised and completely avascular tissues in close apposition. This specialized anatomy requires tight regulation of the balance between vascular quiescence and vascular growth. Retinal vascularization is a coordinated interaction of vascular cells, including endothelial cells, pericytes, and astrocytes, and a balanced production of positive and negative regulatory factors. Angiogenesis plays a crucial role in disorders responsible for most blindness; such as diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration, as well as a large number of other eye conditions. Studies of retinal capillary endothelial cells have shed light on the earliest stages of diabetic retinopathy; but also in other diseases of the retinal microvasculature. Human retinal endothelial cells will surely continue to provide an in vitro model in the pathophysiological studies of vascular diseases in the human eye.