The available x-ray brightness from accelerator-based light sources has been increasing at a rate faster than Moore’s Law. This is enabling new developments in x-ray tomography, using nanoscale x-ray beams on materials ranging in size from micrometers to centimeters. With scanning, one can record x-ray diffraction patterns to view nanoscale structure beyond the optic resolution, or fluorescence signals to study elemental distributions in three dimensions. These approaches are being used in various applications, for example, to study the redistribution of intrinsic metals in biological cells and tissues during biological processes, to compare as-fabricated versus as-designed integrated circuits, and to see the domain structure of soft ferromagnetic materials. While some applications face challenges, including radiation dose, new developments in sparse sampling and reconstruction algorithms, along with a new generation of diffraction-limited storage rings, offer exciting opportunities for materials research.