Pillows are a kind of sleep tool. It is generally believed that pillows are fillers that people use for their sleep comfort. From the perspective of modern medical research, the human spine is a straight line from the front, but has a curve with four physiological curvatures on the side. In order to protect the normal physiological curvature of the neck and maintain normal physiological activities during sleep, pillows must be used during sleep. The pillow is generally composed of a pillow core and a pillowcase.