Therapeutic normalization of blood glucose levels without the danger of hypoglycaemia in patients with diabetes mellitus is only achievable by the regeneration of a functional endogenous insulin secretion. New sources of insulin-producing cells are needed to overcome the limited availability of islet tissue for transplantation to diabetic patients. Engineering of murine or human transformed beta cell lines has progressed slowly in recent years, while significant achievements were made in the differentiation of insulin-producing cells from embryonic and adult stem cells. Some of the results have been questioned, however, and the generated cells lack many characteristics of differentiated beta cells. Therefore, a much better understanding of the processes that govern the expansion and differentiation of beta cells and of pancreatic stem cells is needed. Within the Competence Network for Diabetes mellitus (,Kompetenznetzes Diabetes mellitus') which is funded by the German Federal Ministry of Education and Research, the research consortium AKROBAT focuses on the investigation of molecular mechanisms that regulate pancreatic beta cell and stem cell proliferation and differentiation for the development of stem cell based therapies for diabetes mellitus.