Structural investigation of biological complexes at near atomic resolution is essential to illuminating the molecular mechanism of biological systems under physiological and pathological conditions; these efforts ultimately lead to developing therapeutics and improving human health. Understanding lipid-protein interactions, protein-ligand interactions, multi-subunit protein assembly, and physiologically relevant conformational ensembles require experimental measurement and structural determination, because these are questions too complex to solve in silico even with today’s most advanced structural prediction and simulation software. Single particle analysis (SPA) cryo-EM is used extensively for structural determination at Vanderbilt investigators to illuminate novel mechanism underlying DNA replication (Chazin and Eichman), nuclear export of mRNAs (Ren), calcium signaling (Karakas), host-pathogen interaction (Cover, Crowe, Lacy, and Wan), therapeutic antibody development (Crowe), membrane trafficking (Jackson), neuronal signaling (Nakagawa and Zhou), biomimetic polymers (Duvall), energy homeostasis (Lepesheva), and membrane protein biology of GPCR, ion channels, and transporters (Hamm, Karakas, and Nakagawa). Furthermore, technological advance in cryo-electron tomography enabled visualization of macromolecules in subcellular compartments in situ, providing access to intact ultrastructure of synapses (Zhou) and viral assembly mechanism in host cells (Wan). Essential to these discoveries are the extensive trial-and-error efforts to optimize and identify specimens most suitable for high resolution analysis using the state-of-the-art Titan Krios. This process is often referred to as specimen screening, which requires visualization of negative stain specimen by a 100-200kV transmission electron microscope (TEM) equipped with a detector suitable for image acquisition and subsequent data processing to address specimen quality. We have been extensively using two old TEMs equipped with outdated technologies, 100kV Morgagni and 200kV Tecnai-F20 (TF20), for screening. However, all components of Morgagni and the detector of TF20 are out of replacement parts. Adding a modern detector to TF20 will not add usage hours, yet be prohibitively costly. Considering the low cost-benefit of upgrading TF20 and our inability to repair the Morgagni, we propose to retire the two old TEMs and acquire the modern 120kV TEM, Talos L120C, as a replacement. Talos L120C will provide additional ability to image vitrified samples at cryogenic temperatures in the instance where our cryo- TEM Glacios, used for screening vitrified specimen, is temporarily down for repair. Collectively, the Talos L120C, which will be housed in the cryo-EM core facility and used by the investigators from four Schools and Colleges at Vanderbilt, will fulfill the needs currently met by the retiring TEMs and further establish a robust cryo-EM workflow pipeline to advance the NIH funded projects aimed to i...