In 2020, islet transplantation started to be covered by insurance, and patients with type 1 diabetes had a new therapy. However, the problem of donor shortage remains. We have succeeded in mimicking the islet structure, including not only insulin-secreting cells (pancreatic β-cells) but glucagon-secreting cells (pancreatic α-cells), using iPS cells. We are committed to delivering islet transplantation to all patients with type 1 diabetes in the world while making the most of iPS cell technologies to mass produce homogeneous, highly pure islet tissues.