It is now clear that the local coordaintion of a „Single-Atom„ strongly affects its catalystic properties. In this talk, I will discuss examples from our recent work utilizing Fe3O4, Fe2O3, and TiO2 model supports, where the structure is precisely known and the local geometry can be determined [1]. Using a combination of atomcally resolved imaging, spectroscopy, and theoretical computations, I will show how the adsorption behavior of reactants can be understood by analogy to coordination complexes utilized in homogeneous catalysis [2]. Finally, I will utilize time-lapse STM movies to show how metal adatoms can be both stabilized and destabilized by adsorption of reactants and other molecules in a reactive environment [3] . References [1] R. Bliem et al., Subsurface cation vacancy stabilization of the magnetite (001) surface. Science 346, 1215-1218 (2014) [2] J. Hulva et al., Unraveling CO adsorption on model single-atom catalysts. Science 371, 375 (2021) [3] Z. Jakub et al., Local Structure and Coordination Define Adsorption in a Model Ir1/Fe3O4 Single-Atom Catalyst. Angew. Chem. Int. Ed. 58, 13961-13968 (2019). Acknowledgments Work funded by ERC Consolidator Grant 864628 and FWF CoE MECS.