Cover legend: Hindbrain of a 3-d-postfertilization transgenic zebrafish embryo in which motor neurons express egfp (green), and oligodendrocytes express DsRed2 (red). Abducens motor neurons and commissural axons were labeled using Zn8 immunocytochemistry (blue). For more information, see the article by Zannino and Appel in this issue (pages 2322–2333).