The zebrafish eye has color photoreceptors sensitive to red, green, blue, and ultraviolet light.  In the adult, these photoreceptors are organized in a geometric mosaic pattern across the back of the eye.  We marked blue photoreceptors in this zebrafish with a protein that fluoresces red.  A specialized junction between photoreceptors is labeled here with a molecular marker that appears turquoise.  The combination of the fluorescent photoreceptor and the junction marker demonstrates the striking periodic pattern of photoreceptors.  Understanding the molecular mechanisms involved in generating this spectacular pattern in the zebrafish retina will help us understand the cell-cell communication programs involved in the development of the central nervous system.