For several decades the pathobiology of diabetic retinopathy has been the object of conjecture and hypotheses. Indeed, very little was known about the cellular events triggered by diabetes in the retina and about the processes underlying the microangiopathy. In the last few years there has been a concerted effort to acquire such information, and the work has targeted not just the retinal vessels but more comprehensively the retina. The picture emerging is one of multiplicity: multiple cell types in the retina are affected early by diabetes and multiple processes are operative in the microangiopathy. The main abnormalities captured to date are altered expression of several genes, apoptosis, microthrombosis, and proinflammatory changes. The new information needs to be integrated into temporal and mechanistic sequences and further expanded but it is beginning to provide a framework for the cellular dimension of diabetic retinopathy. [Diabetologia (2001) 44: 791–804]