This picture is a pseudocolored image of an embryonic day 7 chicken retina. The retina has been subjected to in
situ hybridization to visualize cells which express chicken achaete-scute homolog-1 (CASH-1). Clusters of CASH-1-expressing cells, shown in red, are periodically distributed in the central,
more mature region of the retina, shown at the bottom. Clusters contain fewer CASH-1-expressio cells and are less well organized moving away from this area.