BODIPY 581/591 C11 is a fluorescent probe for detecting lipid peroxidation and oxidative stress in living cells. It shifts emission from 591 nm (red, reduced form) to 510 nm (green, oxidized form) upon oxidation. With high sensitivity, low cytotoxicity, and good light stability, it is widely used to study lipid peroxidation and antioxidant properties in living cells or to detect ferroptosis by reacting with hydroxyl radicals.