In type 2 diabetes mellitus, the insulin producing pancreatic beta cells fail to work properly. But we still do not know why they fail. Early in the disease, Incretin hormones can reverse beta cell failure. We examine how incretin hormones work and use them  as tools to peer into the beta cells and to find what may be defective. I will give a brief overview of what we know so far and show you a few exciting new findings from my laboratory.