The molecular approach to single-site and nanoparticle-based heterogeneous catalysts relies on a stringent control over the surface chemistry, enabled by the judicious choice of dehydroxylated supports and tailored organometallic precursors. Aided by the advanced characterization methods, the field of surface organometallic chemistry (SOMC) has provided molecular-level insights into the mechanism and the nature of active sites of various industrial catalysts. The development of SOMC over the last decades yielded supported catalysts outperforming their homogeneous precursors and provided design principles for catalyst development. Applying the rational structure-activity approach of homogeneous catalysis to the surface species leads to further advances of SOMC, including functional materials for sustainable chemistry, energy storage and imaging, to mention just a few. [GRAPHICS] .