Cover picture: Horizontal sections of a pair of olfactory bulbs of adult transgenic zebrafish, in which red fluorescent protein (RFP; magenta) and yellow fluorescent protein (YFP; green) are expressed in the ciliated and microvillous olfactory sensory neurons, respectively. The two distinct types of olfactory sensory neurons project their axons to different regions of the olfactory bulb in a mutally exclusive manner. For details, see the article by Sato et al. in this issue (pages 4889–4897).