A novel type of catalysis, neither homogeneous nor heterogenous, is presented. This new "mesogeneous catalysis" combines the high efficiency characteristic of the homogeneous process with the advantages of the heterogeneous one (i.e., the possibility of removing and reusing the catalyst and obtaining catalyst-free products). The reactions are performed on the surface of nano-particles, where catalytic-active sites have been previously chemically anchored by a short dangling organic chain, thus forming a nano-hybrid system.