Cover legend: This image shows embryonic neuromuscular junction (NMJ) innervation in mice. Whole-mount diaphragms were stained with alpha-bungarotoxin (blue) to detect acetylcholine receptor clusters and a mixture of antibodies against neurofilament and synaptophysin (yellow) to label axonal branches and nerve terminals, respectively. Synapses are restricted to a narrow band in the middle of the muscle. This pattern is severely disrupted when the Wnt-interaction domain of MuSK, a tyrosine kinase receptor, has been deleted, indicating a critical role for Wnt-MuSK signaling in NMJ formation. For more information, see the article by Messéant et al. (pages 4926–4941).