In order to tailor nanoparticles in such a way that they can catalyze certain reactions selectively and efficiently, researchers need to determine the properties of single particles as precisely as possible. So far, an ensemble of many nanoparticles is analyzed. The problem of these investigations is that the contributions of different particles interfere, so that the properties of individual particles remain concealed. Researchers have now developed a novel method in order to observe single nanoparticles before, during and after an electrochemical reaction.