In fish and other animals, the color detecting cone cells in the retina are arranged in specific patterns, and this is believed to be important for allowing animals to properly sense their surroundings. Now, in research published in Physical Review E, an interdisciplinary group of physicists and biologists have used a mathematical model to determine how the cone cells in zebrafish—a common experimental fish model—are arranged in a specific pattern in all individuals. It turns out that small defects in the patterns lead the cells to arrange themselves into only one of two possible patterns that might otherwise emerge.