Fast-acting serum features Retinol Tri-Active Technology: a fast-acting retinoid, a time-released retinol and a retinol booster to minimize irritation and maximize visible results. Retinol can be used in your 20s for preventative measures and for correction as you age. Potent yet gentle formula has minimized side effects typically associated with retinol; even tested safe for sensitive skin. Cruelty-free: always tested on people, never on animals.