Research overview: the cellular tapetum and riboflavin-rich crystals in cats

Cats possess a tapetum cellulosum, a type of reflective layer built from regular arrays of crystal-containing cells rather than the fibrous form seen in some other animals. This survey reviews studies of its ultrastructure, including reports that feline tapetal crystals are rich in zinc and the amino acid cysteine, and discussions of riboflavin involvement. The orderly stacking of these reflective elements acts like a biological mirror tuned to bounce light efficiently back toward the photoreceptors. The overview connects this microanatomy to the tapetum's optical performance and to the characteristic color of cat eyeshine. Understanding the cellular composition matters because it links the macroscopic phenomenon of night-time eye glow to specific molecules and structures. The feline tapetum cellulosum is a well-studied example of how organisms exploit ordered nanostructures and crystals to manipulate light.