Diabetes mellitus is a metabolic disorder characterized by dysfunction, loss, or insufficient mass of β cells. The main function of β cells is to produce and secrete insulin, the hormone responsible for the regulation of blood glucose levels. Type 1 diabetes (T1D) results from autoimmune destruction of β cells, while type 2 diabetes (T2D) mostly results from β-cell dysfunction or peripheral tissue resistance to insulin, often culminating in β-cell death. Thus, both forms of diabetes can benefit from restoration of β-cell mass. Currently, islet transplantation is the only way to provide new β cells to diabetic patients, but the scarcity of compatible cadaveric donors makes this approach available to only few patients; moreover, it requires lifelong immune suppression