This application for a 1-year extension aims to ensure the continued career development of a diverse and exceptionally well trained group of pediatric endocrinologists entering the field of pediatric diabetes research through a joint institutional career development program at Boston Children?s Hospital and the Joslin Diabetes Center. Through mentored training of pediatric endocrine scholars who have completed fellowships in pediatric endocrinology, this joint program will support and nurture career development of junior faculty in biomedical and behavioral diabetes investigations relevant to pediatric diabetes. Based upon the longstanding history of collaboration between Children?s and Joslin, our extensive diabetes research programs, and our record of successful career development of pediatric endocrinologists becoming independent diabetes researchers with support over the last ~15 years from our K12 career development program for pediatric diabetologists, we will continue to mentor pediatric endocrinologists likely to become the future leaders of pediatric diabetes programs in the USA. We will provide career development and support for an additional 1 year for 3 K12 scholars as they prepare to pursue independent investigation in the future. Children?s and Joslin have an extensive group of faculty mentors, multi-disciplinary training programs, commitment to mentoring predoctoral students, post- doctoral fellows, and junior faculty in research relevant to diabetes, and a talented pool of diverse, committed candidates for re-appointment to the K12 program. The rationale for the application includes: increased occurrence of type 1 and type 2 diabetes in childhood, need to discover the causes of type 1 and type 2 diabetes, challenges of achieving target glycemic control in youth, high risk of short- and long-term diabetes complications, outstanding diabetes research at both institutions, need for research to increase understanding of uncommon genetic forms of diabetes, demands of implementing and maintaining intensive insulin therapy and new monitoring technologies in youth, opportunities with automated insulin delivery, and need for trained and committed pediatric diabetes investigators to advance research aimed at treating, preventing, and curing these disorders. Further, while the Covid-19 Pandemic may have slowed efforts, it never halted research progress for our K12 scholars; nonetheless, an additional year of K12 support will solidify their opportunities for future independent funding. Given the history of diabetes research at our institutions and the richness of the Harvard Medical School environment, this joint application offers a unique setting for career development of pediatric endocrinologists in diabetes research. Co-PI and Program Director Lori Laffel MD MPH and Co-PI Morris White PhD, supported by an Advisory Committee, are in optimal positions to continue this effort. Career development is enhanced by Joslin?s NIH-supported Diabetes Research Center (DRC) and Harvard?s Catalyst Program. We have shown the ability to attract highly qualified candidates to our training programs and will continue to nurture the careers of pediatric endocrinologists in pediatric diabetes investigation.