The experimental elucidation of the structures at the interface between a working catalyst and the reacting molecules is the key to a fundamental understanding of heterogeneous catalysis. Researchers from the Fritz Haber Institute of the Max Planck Society have reassigned the vibrational spectrum of vanadium pentoxide, an important catalyst for the synthesis of valuable products through the reaction of organic molecules with gas-phase oxygen, and have thus been able to elucidate which centers are involved in the activation of the oxygen molecule and the oxidation of hydrocarbons.