DESCRIPTION (provided by applicant): This request is for funds to purchase a Nikon super-resolution SIM system on a Ti inverted microscope. This instrument will be housed within the Center for Biologic Imaging (CBI) at the University of Pittsburgh School of Medicine. The mandate of this core facility is to provide access to a full range of light and electron optical, image analysis, and morphometric methods to all research groups within the University of Pittsburgh School of Medicine. Over the last few years super-resolution systems have become functionally useful in biomedical research, improving the resolution limit of light microscopy significantly. However, most of these approaches (STED, PALM/STORM) cannot be used with generically available fluorophores. High resolution methods (specifically Structured Illumination Microscopy (SIM)) which can be used with any currently available fluorophores, from organic dyes to genetically encoded proteins have only recently become commercially available in a "core suitable" format. Because of this and the fact that several of the investigators at our institution have real questions that truly benefit from the improved resolution available we are submitting this proposal. There are no other "core" super-resolution instruments in Pittsburgh. There is one CW STED instrument in a single investigators private laboratory, this cannot be used by other investigators. The requested microscope will be placed in the core laboratories of the CBI, and will be generally available to all NIH funded users of the Center. It is important to recognize that the CBI has two applications in this competition for microscopes. The other application, for a standard confocal will be placed in the new imaging core (a CBI satellite) in th University of Pittsburgh Cancer Institute. There is absolutely no redundancy between the two applications. Since the CBI commenced operations 20 years ago, it has become an integral part of the medical research community currently participating in research projects with more than 200 PHS funded groups within the medical area, as well as in PHS supported projects with investigators in other departments and at neighboring institutions. The device requested here is a critical component of the continued growth of this institutional facility.