would have superior catalytic performance over metal oxide nanocrystals (diameter = 2-10 nm). To test this, we take the previously reported esterification of oleic acid as catalytic model system. We synthesized 3 nm tetragonal zirconia nanocrystals, and functionalized their surface with oleate ligands. Zr12-oleate clusters are the atomically precise, smallest conceivable prototype of such nanocrystals. In addition, the catalytic model system using oleic acid as catalytic substrate, avoiding competition between ligand and substrate for the surface sites. To compare the efficiency of the two catalysts, we added in both cases 10 mol% Zr to the reaction mixture. We monitored the reactions for the first 5 hours by taking aliquots and quantifying the ester product via NMR, see Figure . The oxo clusters are clearly more catalytically active than the nanocrystals, confirming our hypothesis. We do not necessarily ascribe this effect to a special intrinsic activity of the cluster. The cluster has simply every zirconium atom available at its surface. In nanocrystals, most of the zirconium atoms is buried inside the nanocrystal core and unavailable for catalysis. Our experiment is a fair comparison since the catalyst cost scales with the amount of zirconium in the flask. These results thus show that fatty acid capped oxo clusters are an exciting materials class and they can possess advantages over their larger relatives; oxide nanocrystals. One can thus consider (oxo) clusters for many more catalytic reactions that are currently performed with nanocrystal catalysts. As atomically precise nanocrys-tal prototypes, the oxo clusters are also better suited for mechanistic studies compared to nanocrystals which feature polydispersity and a more irregular surface structure.