Bed is a place to sleep, if people want to get a good night’s sleep, the bed is certainly important. From the point of view of the evolution of the bed, the ancient times, people casually lying on the ground to sleep, there is no concept of bed. Later people on the ground to pile up the leaves, they lie on the leaves which is the initial formation of the concept of the bed. After the hunting, put the animal skins on the ground, people lie on the fur another step forward. Then, using wooden boards, wooden strips around a frame, put feathers, leaves, animal skins and other things on the board, people lying in the wooden frame, this is the real sense of the bed, and the location of the bed began to be fixed. From the plank bed, brown bed, rattan bed, spring bed, air bed to water bed, human bed more and more advanced, more and more fine, but also more and more comfortable, the purpose is to sleep comfortably, sleep peacefully. The length of a modern single bed is about 2 meters, about 0.8 meters wide, double bed small about 2 meters long, 1.3 to 1.4 meters wide, large about 2 meters long, 1.6 to 1.8 meters wide. Such a length and width with enough to make a person or two people have room to move when sleeping, not to disturb others or fall to the ground when turning over. From the point of view of the evolution of the bed, at present to sleep spring bed (Simmons) as the most common, but also the most accepted, but in the selection of Simmons to pay attention to: it is best to see the inner structure, so more at ease. Springs should each be very sturdily connected, to maintain an upright position, will not be pulled next to the weight of the spring to lie down. The spring should be attached to the wood strip below, and the padding above should be thick enough so that a person lying on it does not perceive a spring coil. The padding is generally made of foam, at least 10 cm thick. The cover cloth outside the liner should be flat and smooth, not with burrs. Finally, the edge of the Simmons should be reinforced, so that people sitting on the edge of the bed does not fall off. Simmons has a method to determine the appropriate degree of softness, that is, when the person is lying on its side, the spine can maintain a straight posture. If Simmons is too soft, the spine will become U-shaped bend due to pelvic sink; if too hard, the shoulders and pelvis will not sink, the result is that the thoracic vertebrae sink into an irregular S-shaped, which can cause spinal pain and discomfort. Recently introduced abroad water bed, filled with water in the mattress, really soft. However, some people think that sleeping on the water bed in the turn over the feeling of seasickness, and in serious cases, vertigo, vomiting, so not very practical.