Chitons – Acanthopleura granulate – are marine molluscs with hard shells. Remarkably, they also have up to 1000 eyes, each a little smaller than a printed period, but there had been doubts as to their degree of functionality. Christine Ortiz of MIT, US, and colleagues demonstrated that they can indeed form images and have photosensitive cells below them forming a sort of retina. They also found that the lenses are made of large crystallographically aligned grains of the same material that makes up their armour: aragonite, a form of calcium carbonate (the other natural form being calcite).