Project Summary We are requesting funds to purchase an Abberior Facility-line STED microscope for the Advance Cell Imaging Core (ACIC) at the Medical College of Wisconsin (MCW). This instrument will serve a primary user group of 14 investigators, most of whom are well-funded by NIH. These investigators study a variety of projects across diverse fields in cell biology, neuroscience, endocrinology, microbiology, cancer biology, and drug discovery. A common feature of these research projects is the deep reliance on microscopy to understand how molecule- scale structures dictate cell- and tissue-scale function. However, these investigators are facing a major barrier: the lack of access to a suitable super-resolution imaging system to resolve and monitor the nanostructures of interest. STED microscopy is an ideal solution over other super-resolution strategies (e.g., PALM, STORM, SIM, and ExM) for this research community because it operates similarly to confocal as a turn-key system and provides about a 5-fold or higher resolution increase. Many users in this group have ample expertise in confocal microscopy and quantification, making STED implementation easier. Abberior 3D-STED provides not only excellent resolution but also combines the latest innovations that facilitate super-resolution imaging in thicker tissues and live cells. As there is no single STED microscope in our medical school and other universities in Milwaukee, its acquisition will significantly propel the research progress across multiple departments, programs, and institutions in southeastern Wisconsin. This instrument will provide mechanistic understandings of diverse biomedical topics, such as synapses, ion channels, receptor function, autophagy trafficking, mitochondrial dynamics, intracellular signaling, cell migration, organ development, and neurodegeneration. These projects will benefit from access to this STED nanoscope. This instrument will be installed at the imaging core (ACIC) and maintained by the experienced, PhD-level staff. Together, the acquisition of the Abberior 3D-STED microscope will promote new understandings of cellular structures, dynamics, and function at the nanometer scale, which is highly relevant to human health and disease. This instrument will significantly accelerate NIH-funded research programs at MCW and other institutions in the region. This application responds to PAR-22-079 “High-End Instrumentation (HEI) Grant Program”