A research team has visualized the three-dimensional structure of the surface of catalyst nanoparticles at atomic resolution. This structure plays a decisive role in the activity and stability of the particles. The detailed insights were achieved with a combination of atom probe tomography, spectroscopy and electron microscopy. Nanoparticle catalysts can be used, for example, in the production of hydrogen for the chemical industry. To optimize the performance of future catalysts, it is essential to understand how it is affected by the three-dimensional structure.