Type 1 diabetes (T1D) affects 1.4 million people in the U.S. and its incidence has doubled over the past 20 years. The Diabetes Autoimmunity in the Young Study (DAISY) will estimate overall burden of T1D and other autoimmune diseases in the general population by age 30. The study will evaluate environmental risk factors for development of islet autoimmunity and progression to T1D.