Project Summary/Abstract The National Center for X-ray Tomography (NCXT) is a full-service, user facility for biomedical imaging and research. NCXT Users, whether working on site or remotely, have access to specialized microscopes and imaging techniques, in particular soft x-ray tomography (SXT) and super-resolution cryogenic fluorescence tomography (SR-CFT). In the US, these imaging modalities are only available at the NCXT. SXT microscopes visualize and quantify the mesoscale organization of biological cells, including large eukaryotic cells. No stains or contrast agents are required for SXT imaging. Before being imaged by the NCXT's transmission soft x-ray microscope at the Advanced Light Source, cells are rapidly cryo-preserved; the only pre-imaging step required. SXT is highly complementary to other imaging modalities, particularly fluorescence and electron microscopies. Mesoscale, 3D SXT reconstructions of an entire cell act as a framework for the interpretation of other types of imaging and biophysical data, allowing them to be viewed in the context of the whole cell. XM2 is currently the only microscope of its kind in the Nation. The requested P30 funding will support the day-to-day operation of XM-2, together with the associated user program and specimen preparation laboratories, and a program of upgrades to our software/computing resources. During the funding cycle, we will achieve the following specific aims: Aim 1: Give the biomedical research community access to soft x-ray tomography (SXT). The work of this aim ensures imaging cells by SXT remains an option open to US researchers. Significant consideration will be given to making the Resource as user-friendly as possible, particular towards the community of researchers that work remotely. Aim 2: Maintain and calibrate XM-2, the NCXT operated soft x-ray microscope at the ALS. As with all synchrotron beamlines, XM-2 is a sophisticated instrument that requires regular maintenance and calibration. We will take a programmatic approach to ensure XM-2 is robust, reliable, and operates with minimum unscheduled downtime. Aim 3: Implement upgrades and enhancements to ensure the NCXT remains `state-of-the-art.' Over the timescale of the funding cycle, new hardware, software, and algorithms will become available, and some existing components will reach their end-of-life. We will, therefore, carry out upgrades and enhancements to maintain the NCXT at the `state-of-the-art.'