High-resolution transmission electron microscopy (HRTEM) is a powerful tool for atomic scale investigations of catalytic nanoparticles. The dynamics of such catalytic nanoparticles are highly dependent on the environment: temperature, reactant gases and reactor pressure. It is possible to imitate such conditions in a transmission electron microscope (TEM). Electron beam effects play a substantial role in the interpretation of data produced in TEM investigations. There is a trade-off between optimal signal-to-noise ratio (SNR) and minimal beam damage. The current model system consists of gold nanoparticles supported on cerium dioxide. The aforementioned studies elucidate how the nanoparticles undergo changes with observation time and reactant gases present, and surface events as function of dose rate, respectively.