This is a proposal to establish a laser confocal fluorescence microscope at the Friday Harbor Laboratories of the University of Washington. It will be used by several NIH supported resident research programs and, as well, by other visiting investigators from U.S. and overseas institutions. We propose combining a BioRad MRC-600 confocal system and a Zeiss Axiovert microscope for qualitative and quantitative imaging of structurally complex sections, whole mount and living material. Specific examples of work proposed are: 1) (A. Gordon) Localization of fluorescently labelled troponin C and myosin regulatory light chain in skinned muscle fibers will be used to determine molecular mechanisms of regulation of muscle contraction. 2) (J. Blinks) A study of inositol triphosphate-induced release of CA++ in skinned muscle fibers. Is IP3, acting as an intracellular chemical messenger, the """"""""missing link"""""""" in excitation contraction coupling? In a separate project, the photocytes of luminescent cnidaria will be studied to determine the subcellular localization of the green fluorescent protein. 3) (A.O.D. Willows) Developmental tracking of fluorescence-labeled neurons and axonal processes having serotonin and peptide antigenicity will be used to answer questions about the assembly of neural subsystems during ontogeny of the central nervous system. The instrument will also support the work of many other investigators whose research is directly dependent upon the biological resources and instrumentation of the Friday Harbor Laboratories. FHL, located 75 air miles NW of Seattle on San Juan Island, is the marine biological laboratory of the University of Washington. It serves as a national and international resource for diverse marine scientists interested in topics including cell and molecular biology, physiology, and biomedicine.