When Vertex Pharmaceuticals announced last month that its investigational stem-cell-derived replacement therapy was, in conjunction with immunosuppressive therapy, helping the first patient in a Phase 1/2 clinical trial robustly reproduce his or her own fully differentiated pancreatic islet cells, the cells that produce insulin, the news was hailed as a potential breakthrough for the treatment of Type 1 diabetes. For Harvard Stem Cell Institute Co-Director and Xander University Professor Douglas Melton, whose lab pioneered the science behind the therapy, the trial marked the most recent turning point in a decades-long effort to understand and treat the disease. In a conversation with the Gazette, Melton discussed the science behind the advance, the challenges ahead, and the personal side of his research. The interview was edited for clarity and length.