We have developed a state-of-the-art x-ray microprobe with many unprecedented capabilities for a broad range of scientific applications. The combination of the high brilliance third-generation synchrotron radiation sources and the development of high performance x-ray focusing optics have led to the construction of a x-ray microprobe at Argonne National Laboratory with a FWHM focal size less than 0.25 μm and photon flux exceeding 5×l010 photons/cm2/sec/0.01% BW. The microprobe is very flexible and versatile and can be used simultaneously to perform x-ray diffraction microscopy, fluorescence microscopy, spectromicroscopy, and 3D tomography with submicron spatial resolution. It has been used for a broad range of applications since its commissioning in December of 1996. For example, it was used in the study of the symbiotic relation between plant root and fungi, platinum-based anticancer agents, integrated laser/modulator microdevices, electromigration in Al wires in semiconductor devices, and submicron spatial resolution threedimensional tomography of a single cell. The capabilities of the microprobe are described below, and applications using these capabilities will be presented.