This proposal requests funds to purchase a Nikon A1Rsi resonant spectral confocal microscope with high spatial and temporal resolution, focus-maintenance and environmental control for imaging both live and fixed biological samples. This advanced state-of-the-art confocal microscope will be a shared resource, located in a well-established, multi-user, light and electron microscopy facility at Stanford University: the Cell Sciences Imaging Facility (CSIF). This facility is accessible to Stanford University's entire research community. The requested confocal microscope will support NIH funded projects from 9 major users. These projects investigate a wide range of NIH supported research applied to both live and fixed biological samples, including: (1) Regulation of stem cell renewal and differentiation (Drosophila, Fuller); (2) Molecular mechanisms of viral replication, assembly and egress from infected cells (mice, human, Arvin); (3) Analysis of neural development in the visual pathway (mice, rat, Shatz); (4) Pulmonary hypertension in genetically modified mice (mice, Rabinovich); (5) Molecular mechanisms underlying epithelial cell rearrangements in gastrulation (fish, Nelson); (6) Engineering 3D in-vitro niches to reveal fundamentals of cellular biomechanics (human, Heilshorn); (7) Primary cilium biogenesis and membrane trafficking in ciliopathies (human, Nachury); (8) Characterization and modeling of the neuronal mechanisms underlying the development of epilepsy (mice, rat, Prince); (9) Dynamic analyses of stem cell division and fate (human, Blau). These studies investigate critical functional and structural questions in a variety of model organisms and human tissues. This biomedical research impacts diverse aspects of human health and disease, ranging from stem cell development to understanding the cellular and molecular basis of sensory biology. All require state-of-the-art confocal instrumentation for imaging both fixed and live samples which is most effectively provided by the requested Nikon A1Rsi resonant spectral laser-scanning confocal microscope equipped with spectral detector for signal unmixing, resonant scanner and piezo z-drive for fast imaging, environmental control with focus maintenance for drift free time lapse imaging of samples.