Cover legend: Venus YFP was coelectroporated with control vector into the chick neural tube in ovo at stages 12-15. The electroporation procedure was essentially done as described previously (Liu et al., 2004). Embryos were isolated at stage 23 and examined for YFP fluorescence. The spinal cord showing green fluorescence was isolated as an open-book preparation and the whole mount immunostaining was carried by using the chicken commissural axon marker, anti-axonin-1 antibody. The merged image shows commissural axons project toward the floor plate with most of them arriving at or crossing over the floor plate. For more information, see the article by Liu et al. in this issue (957–968).