Nudibranchs are often referred to as the butterflies of the sea. Nudibranchs live worldwide, primarily in warm, shallow marine regions, and stand out for their flamboyant colors and diverse shapes. A team from the Max Planck Institute of Colloids and Interfaces in Potsdam and the University of Cambridge has now discovered how they create their colorful patterns. According to their findings, published in the Proceedings of the National Academy of Sciences, the color is produced by nanostructures, each of which creates a specific color impression.