X-ray ultramicroscopy in the SEM is a relatively new application in the wider field of X-ray microscopy. This latter field includes synchrotron and cabinet-based systems that vary in their X-ray power, capability, sample size, spatial resolution, and convenience. One important capability of the SEM-hosted X-ray microscope is that the normal SEM imaging and analytical functions such as secondary and backscattered imaging and microanalysis by EDX or WDS are unimpeded. X-ray imaging then serves as a complement to the normal use of the SEM. The convenience of easy access in an SEM lab to an X-ray microscope with 3D tomographic capability makes this an important development.