This study in Science Direct reviews how different types of stem cells—like embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and adult mesenchymal stem cells (MSCs)—have shown potential in restoring or maintaining insulin production and studying diabetes on a patient-specific level. Among these, MSCs are the most studied in diabetes-related trials, while clinical testing of ESCs is still in its early stages. This review highlights the biology and strategies behind using stem cell therapy to treat diabetes.