Essay: Synchrotron X-ray sources are opening up new avenues of research in materials science. Applications include X-ray diffraction of ever-smaller samples, X-ray fluorescence microscopy, and X-ray tomography, a technique which provides detailed information on the internal structure of materials. The potential contribution of the Advanced Photon Source (APS) being built at the Argonne National Laboratory in the USA which should be operational in 1995, and modes of access to the facility are described.