The goal of the current proof-of-concept study is to characterize brain structural, functional, and molecular imaging biomarkers of preclinical Alzheimer's Disease and related dementias (AD/ADRD) neuropathology in a selected group of young adults with youth-onset diabetes (Y-DM; type 1 diabetes \[T1D\], n=5; type 2 diabetes \[T2D\], n=5) from the SEARCH for Diabetes in Youth study cohort, and an age-similar group of young adults without diabetes (n=5). This study will quantify structural and functional imaging biomarkers of AD/ADRD neuropathology via magnetic resonance imaging by assessing gray matter (GM) volume/cortical thickness, as well as GM and white matter (WM) microstructure, resting state functional network connectivity (rsfMRI), and cerebral blood flow (CBF) and WM hyperintensity volume. This study will additionally quantify brain tau density via positron emission tomography as the gold-standard measure of preclinical AD/ADRD neuropathology.