PROGRAM DESCRIPTION This request is for funds to purchase a Leica Tau-Stimulated Emission Depletion (Tau-STED) microscope on the Stellaris 8 platform with 1 depletion line. This instrument will be housed within the Hooker Imaging Center (HIC) in the Department of Cell Biology and Physiology in the School of Medicine at the University of North Carolina at Chapel Hill. The HIC provides access to a full range of light and electron optical, image analysis, and morphometric methods to all research groups within the University of North Carolina at Chapel Hill, including the School of Medicine, College of Arts and Sciences, and other professional schools on campus. Super-resolution microscopy is an essential advancement in optical microscopy techniques in biomedical research that has rapidly matured over the last 5 years. Currently on campus, there is a single microscope capable of true super resultion microscopy, to serve the over 350 biomedical research laboratories on campus, and this scope is more than five years old, and cannot perform super resolution in 3 dimensions, in level cell mode, or at distances > 2 µm from the coverslip. Recent dramatic improvements provided by the commercially available Leica Tau-STED microscopy bring higher resolution in all three dimensions, increased sensitivity, and increased suitability for live cell imaging by exploiting changes in fluorescence lifetime following stimulated emission depletion. Furthermore, the commercially available 775 depletion line allows facile and gentle gated two color super-resolution imaging, such that it can be easily deployed in a core environment such as the HIC and accessible to the variety of research projects and labs on campus. The need for this instrument is demonstrated throughout the application with several diverse NIH supported projects in fields including; Neurobiology, Cell Biology, Cardiac Biology Developmental Biology, cytoskeletal biology, basic and disease-oriented protein trafficking biology, RNA and DNA biology. The abilities provided by Tau-STED will transform our fundamental understanding of the biology of these many arenas. Since the HIC began serving the imaging community of UNC 14 years ago, it has become an integral part of the medical research community currently participates in research projects with more than 100 PHS funded groups within the medical area, as well as in PHS supported projects with investigators in other departments and at neighboring institutions. The steering committee of the HIC, and the directors of non- overlapping imaging cores on campus together deem that acquisition of a Tau-STED system as an essential addition to the repertoire of instrumentation available to PHS funded users at the University, and that the HIC is the optimal core to house the scope for reasons described throughout the proposal.