Cover legend: This confocal image of a flat-mounted retina shows retinal ganglion cell axons from wild-type (top) and Sfrp1/2 double knockout (bottom) mouse embryos. Colors reflect the depth of the confocal layer and reveal that mutant axons are not constrained to the fiber layer and the optic disc, as are wild-type axons. Axon misrouting is evident at the optic disc (yellow-green) and in the outer layer of the retina (pink) in the mutant, when compared to the arrayed organization in wild-type. For more information, see the article by Marcos et al. (pages 4729–4740).