The systematic and detailed characterization of heterogeneous catalysts is critical for design of effective and stable catalytic materials since it allows one to understand correlation between their structure and physicochemical properties. Especially it is important to monitor the structural evolution of catalytic materials and their active sites in a controllable environment and under realistic reaction conditions. Thus, we propose to use a powerful combination of aberration-corrected high-resolution TEM and in situ TEM experiments which allow us to gain extensive knowledge about structure‐activity relationships, reaction mechanism and active site evolution under various experimental conditions.