The buzz about nanoparticles! The cover picture represents well-dispersed single-phase Pt3Sn bimetallic alloy nanoparticles of 2.4 nm diameter inside the pores of a honeycomb-structured mesoporous silica. The resulting material is a well-defined heterogeneous catalyst for preferential CO oxidation in the presence of H2 (PROX catalysis). In their communication on p. 1729 ff., Chloé Thieuleux et al. show how to control by sol–gel approach the growth of the silica matrix around preformed single-phase Pt3Sn nanoparticles, and how to remove the template and the stabilizing ligand around the metallic nanoparticles, so that the resulting material is a well-defined catalytic material active in isobutane dehydrogenation and in low-temperature CO PROX catalyses.