The manner in which oxygen binds to gold clusters depends on the number of atoms in the cluster, according to a pair of studies conducted independently. The findings may help researchers understand the surprising catalytic activity exhibited by gold in nanocrystalline form. Considered chemically inactive for ages, gold has demonstrated its catalytic prowess repeatedly in the past decade. Yet it has remained unclear how gold nanostructures bind O2, which activates the molecule for gold’s most studied catalytic trick—oxidation. Now, two research teams have independently determined through experimental and computational methods that anionic gold clusters with two, four, or six gold atoms bind O2 in a nonbridging superoxo (end-on) fashion. Larger anionic clusters with 10, 12, and 14 gold atoms bind O2 in a bridging peroxo configuration. O2Au8– can adopt either of the structures, which differ only slightly in energy. One of the teams was led by André Fielicke of the Fritz Haber Institute in Berlin (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201108958). The other study was led by Lai-Sheng Wang of Brown University and Xiao Cheng Zeng of the University of Nebraska, Lincoln (J. Am. Chem. Soc., DOI: 10.1021/ja302902p).