The cover picture shows the antenna effect, in which a chromophore excited state can sensitize the lanthanide-centered emission by energy transfer via a Dexter mechanism. The dimmer terbium and ytterbium ions show that light hitting the antenna cannot sensitize the emission of these, while the bright red europium can be sensitized by the antenna. In our paper we show that sensitized lanthanide luminescence can only occur if the antenna and the lanthanide ion can collide, and that collisions can be prevented by steric congestion. Details are discussed in the article by T. J. Sørensen, S. Faulkner et al. on page 2165 ff (DOI: 10.1002/ejic.201700027). For more on the story behind the cover research, see the Cover Profile (DOI: 10.1002/ejic.201700299).