This is a proposal for a Zeiss LSM 510 Multiphoton and Meta Spectral Microscope for a facility to study processes in live cells. The investigators in this grant are a highly interactive group interested in a range of areas, including, neurobiology, membrane traffic, developmental biology, and host-pathogen interactions. Collectively, we have accomplished a great deal by localizing proteins in fixed cells. Our next general goal is to study movement of proteins, especially GFP labeled proteins, in live cells. We wish to study these processes in higher-order biological specimens, such as brain sections or developing organs in three-dimensional matrices. These particularly thick specimens cannot be adequately imaged by many techniques that are often used in live cells, such as deconvolution microscopy. Conventional confocal microscopy causes too much phototoxicity. The investigators in this grant are part of a group of 70 UCSF laboratories that are moving to the new Mission Bay Campus. Mission Bay is five miles away from the existing multiphoton microscopes located at the main UCSF Parnassus campus and the Mt. Zion Cancer Center, which prevents adequate access for Mission Bay labs, especially for long-term live cell studies. The existing multiphoton microscopes are also very heavily used, and are inadequate to meet the needs of the rapidly expanding university. Preliminary data confirms that the requested multiphoton microscope will greatly enhance our ability to image processes in live cells. A further advantage of the requested microscope is the newly developed Meta Spectral system. This new system greatly facilitates the use of fluorophores with closely overlapping spectra (such as different variants of GFP) and should significantly enhance the use of FRET.