The stuffing of the duvet is mainly down, and the down is the abdomen of the goose and the duck, and the fluff of the flower of the aloe is called a feather. Because down is an animal protein fiber, it has higher heat preservation than cotton (vegetable cellulose), and the down spherical fiber is densely covered with thousands of triangular fine pores, which can shrink and expand with temperature change, and produce temperature regulation function. It absorbs the hot air flowing from the human body and isolates the intrusion of cold air from the outside.