Bart O. Roep is Professor of Diabetology, Immunopathology & Intervention at Leiden University Medical Center (LUMC) and an internationally recognized expert in type 1 diabetes. He studied Medical Biology in Amsterdam and obtained his PhD in Medicine in Leiden for his research on T cells in diabetes. Since then, he has focused on unraveling the role of the immune system and developing new therapies, ranging from immunotherapy to stem cell and gene therapy. He discovered how T1D develops, that it is not an inherited disease, that many patients continue to produce insulin, and that it is therefore urgent to intervene in the disease process—even years after diagnosis. In addition to his work in Leiden, he is a Visiting Professor at the Danish Diabetes Academy. For his pioneering research, he has received prestigious awards such as the Minkowski Prize, a VICI grant, a Fellowship from the Royal Netherlands Academy of Arts and Sciences (KNAW), and an ERC Advanced Grant.