The advent of high brilliance synchrotron sources has stimulated the development of advanced x-ray microtomography. However, materials research problems challenge existing tomographic techniques. High spatial resolution is required to identify and characterize microstructure in real materials. Good elemental sensitivity is required to study the effects of microalloying. Three-dimensional crystal texture, strain and phase information is required to understand advanced materials. Materials samples can include a wide range of elements, can come in unfavorable geometries, and sometimes require dynamic measurements of their three-dimensional structure. One challenge for x-ray microtomography is the measurement of low concentrations with good spatial resolution and high elemental sensitivity. Another challenge to standard x-ray microtomography is the study of elemental distributions in planar structures where elemental sensitivity is required in one or two dimensions, but the spatial sensitivity in all three dimensions is not required. For a large class of materials, crystalline structure, strain and texture are critical to the materials properties. Recent work has now demonstrated the possibility of extending X-ray microdiffraction to the study of three dimensional crystallographic distributions. Efforts are now underway at the APS, ALS, SSRL and NSLS to further develop x-ray microdiffraction and x-ray microdiffraction tomography. The measurement of strain and texture in three dimensions will have important applications to the study of high J{sub c} high {Tc} superconductors, the study of second phase distributions and texture in composite materials, and the study of crack and void evolution in structural and electronic materials. Another frontier for x-ray tomography is the development of dynamic, real-time measurements
