Hypnum cupressiforme, the cypress-leaved plaitmoss or hypnum moss, is a common and widespread species of moss belonging to the genus Hypnum. It is found in all continents except Antarctica and occurs in a wide variety of habitats and climatic zones. It typically grows on tree trunks, logs, walls, rocks and other surfaces. It prefers acidic environments and is fairly tolerant of pollution. It was formerly used as a filling for pillows and mattresses; the association with sleep is the origin of the genus name Hypnum (from Greek Hypnos).