Coumarin is found in many plants, notably in high concentration in the tonka bean, woodruff, mullein, and bison grass. It has a sweet scent, readily recognized as the scent of newly-mown hay, and has been used in perfumes since 1882. It has clinical medical value as the precursor for several anticoagulants, notably warfarin, and is used as a gain medium in some dye lasers.