Citrus peel is the outer skin of citrus fruits, built in two layers: the coloured outer flavedo — also called epicarp or zest — and the white inner pith, the albedo or mesocarp. The flavedo houses the oil glands that yield citrus essential oils, while the albedo is the commercial source of pectins. Beyond those prizes, peel is rich in fibre and phytochemicals. It is candied for baking, grated fresh as zest, or processed into flavourings. Far from waste, it is a valorised by-product stream — though processors must wash it well, since the outer skin also collects spray residues.