A diverse group of 6 NIH funded investigators and a junior investigator within Departments of Pathology, Biochemistry, Medicine, Microbiology and Immunology at Dartmouth Medical School and Biological Sciences at Dartmouth College request funds to purchase a state of the art multicolor TIRFM live cell imaging system from Olympus America. The system integrates an Olympus IX-81 inverted microscope, an automated multicolor total internal reflection microscopy (TIRFM) illuminator (Olympus Celltirf) equipped with three lasers 405/491/561, and capable of FRAP/ photoactivation;an ultra-fast/highly sensitive sCMOS camera (Andor Neo) coupled to a DualView beam splitter;fully integrated MetaMorph for Olympus acquisition/analysis software optimized for 1) rapid/ultra-sensitive 4D four channel acquisition;2) FRAP and photoactivation and 3) particle tracking;The new state-of-the-art workstation will complement our heavily utilized Zeiss LSM 510 META and aging single channel manual TIRFM system, while constituting a significant upgrade in multi channel acquisition, speed and sensitivity. Importantly, the multicolor TIRFM system will provide new/unique total internal fluorescence capabilities for the Optical Cellular Imaging Facility that s utilized regularly by multiple schools and departments comprising >75 laboratories and ~300 users. Our investigators, all well funded through the NIH, work on a host of cell biological and biochemical questions aimed at understanding molecular mechanisms of fundamental cellular processes such as membrane trafficking, endocytosis, pathogen infectivity and cytoskeletal organization and interaction with the plasma membrane. Satisfactory completion of the stated goals of the NIH-sponsored projects of these users requires examination of dynamic cellular processes in live cells with high spatial and temporal resolution and reduced phototoxicity. The total internal reflection microscope described in this proposal is a state of the art instrument tht satisfies these needs by using proven technology. In the requested configuration, the multicolor TIRFM workstation will afford our disparate group of investigators a broad range of basic/advanced live-cell microscopy capabilities that are presently deficient/absent at Dartmouth. It would represent the only instrument of its kind to serve the entire Dartmouth life science community. The new system will be conveniently located, administered, and maintained, in the Norris Cotton Comprehensive Cancer Center Optical Imaging Core Facility (OICF);and it will be incorporated into the OICF's existing, well established recharge system to ensure recovery of funds for supplies and maintenance.