X-rays were discovered over 100 years ago. Since then they are often being used to “see through” materials and visualize hidden objects, as we know from medical examinations or airport security. In scientific research, X-rays are an invaluable tool to probe properties of materials and a vast range of applications has been established in biology and health science, chemistry, physics, earth and environmental science, archeology and cultural heritage. A special source of X-rays are large electron accelerators that generate extremely brilliant radiation, which is particularly suitable for the investigation of materials on a nanoscopic scale. They make it possible to investigate physical and chemical processes in catalysts, batteries, solar cells and novel storage media in great detail and to answer fundamental questions about infections, photosynthesis or processes in the Earth’s interior.