The cover picture shows a model of a luminescent iridium(III) complex functionalized with three Ac-TZ14011 peptide moieties binding to the chemokine receptor 4 (CXCR4). The G protein-coupled receptor CXCR4 is over-expressed in many types of cancer and, therefore, is a potential biomarker in the field of diagnostic oncology. In the CPK model, the three Ac-TZ14011 peptides are colored by element and the iridium complex is red. The iridium complex has a luminescence lifetime in the order of 200 ns; this enables visualization with fluorescence lifetime imaging microscopy (FLIM). The FLIM image of cells incubated with the peptide–iridium conjugate in the background shows accumulation in the cell membranes; this is in accordance with the membrane location of CXCR4. For further information, see the communication by A. H. Velders, F. W. B. van Leeuwen, et al. on p. 1897 ff.