Advancing molecular-level understanding of (support-)catalyst-adsorbate interaction is crucial to rationalize reaction mechanisms and to facilitate the design of optimal nanocatalysts. As depicted by the Sabatier principle, reagents adsorption on a catalyst should be neither too strong nor too weak in order to achieve an optimal catalytic performance. Although computational and analytical methods have been extensively employed to probe molecular adsorption on nanocatalysts, they are either carried out in vacuum or lack spatiotemporal resolution. The above challenge can be effectively addressed by employing single-molecule fluorescence imaging, which can resolve, at superb spatial and temporal resolutions, molecular adsorption under operando conditions. However, conventional studies have centered on entities or processes that emit fluorescence or are fluorescently labeled whereas most catalytic reactions do not involve fluorescent species. Recently, I developed a new imaging technique that can interrogate non- or weakly fluorescent processes at nanometer resolution, namely adCOMPEITS (adsorption-based competition-enabled imaging technique with super-resolution, manuscripts in preparation). By spatiotemporally quantifying the change in fluorescent signals, the spatial adsorption affinity map of non-fluorescent molecules on a single nanocatalyst can be obtained. In this research direction, we will employ the newly developed adCOMPEITS imaging technique to examine the (support-)catalyst-adsorbate interactions under operando conditions, aiming to revolutionize the mechanistic understanding of heterogeneous catalysis.