X-ray micro-tomography (micro-CT) is a non-destructive imaging technique that provides resolution of material microstructures in three dimensions at scales from hundreds of nanometers to centimeters. The technique is used at NASA Ames Research Center to investigate a variety of advanced materials, including lightweight composite heatshields for atmospheric entry, woven materials, parachute textiles and meteoroids. Data are collected using both synchrotron and laboratory-based X-ray sources. Synchrotron micro-CT is performed in collaboration with the beamline 8.3.2 at the Advanced Light Source at Lawrence Berkeley National Laboratory. High-fidelity digital representations of microstructures obtained from micro-CT are used as framework to perform predictive simulations of effective material properties and material response using high performance computing.