Examples are voltage sensitive dyes and fluorescing proteins. The eyes of some pigeons contain yellow fluorescing pigments known as pteridines. In Europe, Europium and fluorescing dye are combined on Euros. The fraction of fluorescing droplets is recorded. Under UV light, fluorescing fibres are visible on every page except the data page. Laundry detergents may also use fluorescing agents to similar effect. Aegis was eventually developed into a product called "Fluorescing Astral Bacteria-3", or "FAB-3".