Cover legend: A high-powered view of the optic chiasm of a 72 h zebrafish larva that is mutant for the axonal guidance receptor robo2. Loss of robo2 makes retinal axons insensitive to slits, repellents that help guide them across the midline and to their targets. Anterior is to the top, and the eyes are out of frame on either side. Retinal axons are color coded depending on their dorsal-ventral position in the brain, with cool colors indicating ventral levels near the chiasm and warm colors indicating more dorsal levels. Retinal axons sweep towards the center, cross at the ventral midline, travel to the contralateral side of the brain, and then extend dorsally. A variety of profound axonal pathfinding errors can be seen, including ectopic retinal commissures at both ventral and dorsal levels. This projection image was made on a Leica DMIRE2 confocal microscope of a fish in which retinal axons were visualized by GFP expression driven by the Brn3C promoter (a kind gift from the Baier laboratory, University of California, San Francisco). For more information, see the article by Chalasani et al. in this issue (pages 973–980).