Project Abstract Cryo-electron microscopy (cryo-EM) is a powerful technique for determining the structures of macromolecular complexes from frozen hydrated specimens, bypassing constraints imposed by other structural biology techniques like X-ray crystallography and NMR. Cryo-EM relies on imaging individual molecules at high magnification, then averaging together images of hundreds of thousands of copies of the molecule in three dimensions. Cryo-EM is unique among structural biology approaches in being able to resolve different conformational states from a mixed population of molecules, making it ideal to study flexible and heterogeneous macromolecules under near-physiological conditions. Recent technological advances in cryo-EM have generated a quantum leap in achievable resolution, with near-atomic resolution structures becoming routine. This means that cryo-EM has come to rival X-ray crystallography in the accuracy of structures that can be determined, as well as expanding the types of macromolecules that can be subjected to high-resolution structural analysis. These advances have created tectonic shifts in the landscape of structural biology, with some investigators abandoning other structural techniques wholesale and others rushing to adopt the new technologies as a compliment to existing approaches. Two technological developments have driven this shift: a new generation of electron microscopes designed for the unique constraints of cryo-EM with improved optics and higher throughput, and advanced direct electron detectors that dramatically improve the resolution of recorded images. UW has already invested in direct detector technology, and here we are requesting funds to acquire a high performance cryo-electron microscope, the FEI Talos Arctica. The Talos Arctica is a high performance electron microscope designed from the ground up to be used for cryo-EM. Improvements include a constant power objective lens for greater thermal stability and reduced hysteresis, a cryo-autoloader for automated and contamination free specimen transfer, better vacuum system for maintaining specimens without contamination, a piezo stage for improved mechanical precision and stability, and an enclosed platform for better environmental control and stability. The net effect of the improvements embodied in the Talos Arctica is an increased rate of acquisition of higher quality data. The quality, reliability, and throughput of the microscope will broaden the accessibility of cryo-EM for users across campus and in the region. This microscope will enable new lines of research and complement ongoing research programs in fields as diverse as fundamental cell biology and biochemistry, infectious diseases and vaccine development, membrane protein structure, cellular stress responses, metabolism, neurobiology, and cancer.