Fundamental insights into electrode–electrolyte interfaces are crucial for our understanding of electrochemical processes. Standard electrochemical methods, such as cyclic voltammetry, can reveal important information about the systems of interest. Nevertheless, information about structure and morphology of the electrode–electrolyte interface is not that easily accessible. In situ scanning tunnelling microscopy can resolve the electrode as well as the direct interface to the electrolyte in real time during electrochemical measurements. This includes changes of the electrode in the nanometre to micrometre range, for example, during metal deposition or corrosion, as well as the observation of ordered molecular adlayers on the electrode. In this work, we want to highlight the capabilities of such studies to better understand the fundamental processes of electrocatalysis and metal deposition and dissolution, which are essential to electrochemical energy storage systems.