Researchers have pioneered a new technique called X-ray linear dichroic orientation tomography, which probes the orientation of a material's building blocks at the nanoscale in three-dimensions. First applied to study a polycrystalline catalyst, the technique allows the visualization of crystal grains, grain boundaries and defects -- key factors determining catalyst performance. Beyond catalysis, the technique allows previously inaccessible insights into the structure of diverse functional materials, including those used in information technology, energy storage and biomedical applications.