The Cover Feature illustrates the calcination process of rock-salt CoO nanoparticles, which allow for the synthesis of core-shell Co₃O₄@CoO nanoparticles. In their Research Article, S. Schulz et al. demonstrate that the Co(III) cation concentration in the resulting nanoparticles directly correlates with the calcination time, resulting in a steadily decreasing OER activity of the as-formed core-shell Co₃O₄@CoO nanoparticles. More information can be found in the Research Article by S. Schulz et al.