Coronal section of a mouse embryonic forebrain labeled on embryonic day 11 with iododeoxyuridine (green) and bromodeoxyuridine (red). Double-labeled nuclei are yellow. The green (IdU-labeled only) nuclei are daughter cells produced by cell division of neural progenitor cells. For more information, see the article by Fujimura et al. (pages 10908–10919).