RecruitingYouth-Onset Type 2 Diabetes and Heart Disease: The Young at Heart Prospective Cohort StudyBackground: Type 2 diabetes is a disease that affects blood sugar levels. Complications can include heart and blood vessel (vascular) diseases. Rates of type 2 diabetes have tripled in children and young adults over the last 40 years. Vascular diseases are also increasing in young people. Objective: To learn more about factors, including type 2 diabetes, that may cause vascular disease in young people. Eligibility: People aged 12 to 25 years who (1) have type 2 diabetes; (2) are overweight but not diabetic; (3) or are lean and healthy. Biological parents are also needed. Design: Young participants will visit the NIH clinic once a year for up to 25 years. Each visit will take 4 days. Before each visit, participants will wear devices to track their sleep, activity, and blood sugar levels for 7 to 10 days. At each visit, participants will have tests including: Samples: They will provide blood, urine, and stool samples. Heart: They will ride a stationary bike for 6 minutes with stickers applied to their chest. Scans: They will lie on a bed that slides into a tube; the machine will take pictures of the inside of their body. Energy: They will wear a hood over their head to measure the air they breathe. Social stress: They will give a speech for 10 minutes to show their body s response to stress. Glucose: They will drink a sweet drink to see how their blood sugar changes. Biological parents will have 1 study visit. They will have blood tests. They will fill in questionnaires about their lifestyle and stress. ...