The computational limitations are less severe for nanocluster catalysts, and recent computational work in this field has in fact highlighted the crucial role of "fluxionality", i.e. a facile dynamic restructuring, for the reactivity of these clusters. It has been exactly demonstrated that there is no ready separation of time scales and that cluster isomerization processes can occur as frequently as the molecular processes of catalysis. At such a dynamic interconversion, different elementary processes of the catalytic cycle can therefore occur on different cluster isomers. The cluster is not a mere static scaffold for the surface chemistry. Instead, there is dynamic coupling between catalyst reactivity and the operando evolution of the cluster. Catalytic function can only be understood by holistically considering both types of processes on equal footing.