The Kaffir lime (Citrus hystrix) belongs to Rutaceae (the Citrus family). It is a small evergreen tree that is native to tropical Southeast Asia and southern China. This tree grows up to a height of 2-11 m. The leaves are hourglass-shaped, comprise the leaf blade plus a flattened, leaf-like winged petiole. The fruit is rough and green, bumpy, about 4 cm in diameter, and ripens to yellow. Its fruit and leaves are used in Southeast Asian cuisine and its essential oil is used in perfumery.