Cover legend: Sodium channel immunofluorescence in axons of retinal ganglion cells. Bundles of labeled ganglion cell axons (vertical "tree trunks") run across the surface of the retina in this view of a flat-mount retina stained with a pan-specific sodium channel antibody. The intensity scale is inverted so that bright objects appear black. In addition, short segments of intense sodium channel labeling ("tree twigs") are found at the axon initial segments, between the axon bundles. More dimly labeled ganglion cell bodies ("tree leaves") can also be seen. The sodium channels at the initial segment are a distinct subtype, Na_v1.6, which is required for optimal repetitive firing of retinal ganglion cells. For more information, see the article by Van Wart and Matthews in this issue (pages 7172–7180).