Abstract: New biological therapies for type 1 diabetes are emerging from the forefront of stem cell and islet cell biology. Basic research in animal models has uncovered a variety of mechanisms by which natural regeneration of pancreatic islet cells occurs, despite the underlying autoimmune defect. Two mechanisms – in particular, β-islet cell proliferation and stem cell differentiation – can be harnessed in innovative ways in order to regenerate islets lost to disease. This review provides a background on stem cells and describes a range of potential biological therapies for type 1 diabetes, including the use of adult stem cells from the spleen, an organ not previously considered a source of pancreatic stem cells. Stem cells of the spleen have been demonstrated to home to the pancreas, where they mature into fully functional islet cells responsible for restoring normoglycemia. If the underlying autoimmune defect can be eradicated, stem cells of the spleen, as well as related strategies, can be used in order to regrow islets destroyed by type 1 diabetes.