A mattress is a piece of bedding typically consisting of multiple layers of foams and fibers, along with an innerspring unit used to provide support to one's back during sleep. Mattresses are usually used along with a foundation, which might include metal springs or torsion bars on a wooden frame, which supports the mattress. Increasingly, mattresses made with various foam materials such as latex foam, visco-elastic foam and other polyurethane type foam but without metal spring units are becoming common and accepted. Although mattresses are sold with fillings of air, water, or foam, innerspring or coil mattresses currently have over 80% of the market share in the U.S.
Prehistoric humans, simply huddled in groups for warmth at night and slept on the ground or directly on floor boards (in many Asian countries today people still sleep directly on the floor with a simple thin grass mat under them). 10,000 to 8,000 years ago the quest for comfort brought on the invention of the mattress and then the bed. An important change was raising them off the ground, to avoid drafts, dirt, and pests.
Humans began sleeping off the ground, on primitive beds or mattresses they crafted. The first "mattress" was probably a pile of leaves or grass with animal skins thrown over it. With time, humans probably also used straw to sleep on. Then, people started putting the "soft" materials on some kind of cloth (which eventually evolved to be called mattress ticking). The bags or sacks were initially filled with grass, straw, pea shucks, rags, etc.