Cover picture: (Top) Schematic representation of classical signaling by M1 muscarinic receptors (M1R). (Bottom) FRET measurements of individual signaling steps (dots) compared to predictions of a kinetic model of the M1R signaling cascade (numbered curves). (1) Agonist binding reported by intramolecular FRET. (2) G protein binding to the receptor, FRET from M1R-CFP/Gβ-YFP. (3) Nucleotide exchange, FRET from Gαq-CFP/ Gβ-YFP. (4) Gαq binding to PLC, FRET from Gαq-CFP/ PLC-YFP (see article by Falkenburger et al., 81–97).