Unlike animals, which synthesise cytochrome P450 enzymes mostly for the degradation of xenobiotics, plants have evolved a large number of different P450 enzymes for the synthesis of secondary metabolites. Probably the most conspicuous of these secondary metabolites are anthocyanins, which are important flower pigments. The types of anthocyanins synthesised in plants are controlled by the cytochrome P450 enzymes flavonoid 3'-hydroxylase and flavonoid 3',5'-hydroxylase. Cloning of flavonoid 3',5'-hydroxylase genes has enabled the manipulation of anthocyanin synthesis in transgenic plants and enabled the production of novel pigments and flower colours.