Memory foam was developed in ***6 under a contract by NASA's Ames Research Center to improve the safety of aircraft cushions. Ames scientist Chiharu Kubokawa and Charles A. Yost of the Stencel Aero Engineering Corporation were major contributors to this project. The temperature-sensitive memory foam was initially referred to as “slow spring back foam”; Yost called it "temper foam". Created by feeding gas into a polymer matrix, the foam has an open-cell solid structure that matches pressure against it, yet slowly springs back to its original shape.

Yost later founded Dynamic Systems Inc. in collaboration with NASA to commercialize the foam, including it in both medical equipment such as X-ray table pads and sports equipment such as football helmet liners. After Dynamic Systems sold memory foam products to Becton, the range of products was expanded.

When NASA released memory foam to the public domain in the early ***0s, Fagerdala World Foams was one of the few companies willing to work with the foam, as the manufacturing process remained difficult and unreliable. Their ***1 product, the "Tempur-Pedic Swedish Mattress" eventually led to the mattress and cushion company, Tempur World.

Memory foam was subsequently used in medical settings. For example, it was commonly utilized in cases where the patient was required to lie immobile in their bed on a firm mattress for an unhealthy period of time. The pressure over some of their bony regions decreased or stopped the blood flow to the region causing pressure sores or gangrene. Memory foam mattresses remarkably decreased such events.

Memory foam was initially too expensive for widespread use,[citation needed] but in recent years it has become cheaper. Its most common domestic uses are mattresses, pillows, and mattress toppers. It has medical uses, such as wheelchair seat cushions, hospital bed pillows and padding for persons suffering long-term pain or postural problems; for example, a memory foam cervical pillow may alleviate chronic neck pain. Its heat-retaining properties may help some pain sufferers who find the added warmth helps to decrease the pain.[citation needed]

A memory foam mattress is usually denser than other foam mattresses. This makes it more supportive, but also heavier. It is often seen[by whom?] as a good compromise between the comfort of a soft mattress and the solidness of a firm one. Memory foam mattresses often sell for more than traditional mattresses.

The property of firmness (hard to soft) of memory foam is used in determining comfort. Firmness is measured by a foam's indentation force deflection (IFD) rating. However, it is not an accurate measure on "soft" and "firm". A higher-IFD foam, with a lower density can feel soft when compressed.

IFD measures the force (in pounds-force) required to make a dent 1 inch into a foam sample *5" x *5" x 4" by an *-inch-diameter (*0 sq in) disc—known as *@******************** IFD ratings for memory foams range between super soft (IFD *0) and semi-rigid (IFD *2). Most memory foam mattresses are firm (IFD *2 to IFD *6).

Some[according to whom?] report that IFD is a poor way to measure softness of memory foam, and that foam density as a measure of quality is more important, but not always true. Foam density of 5 poundsper cubic foot (*0 kg/m3) or greater is considered high quality, although most standard memory foam has a density of 1 to 5 lb/ft3 (*6–*0 kg/m3). Most bedding, such as topper pads and comfort layers in mattresses is 3 to 4.5 lb/ft3. Very high densities such as 5.3 lb/ft3 (*5 kg/m3) are used infrequently in mattresses.

Memory foam has an open-cell structure that reacts to body heat and weight by 'moulding' to your body, helping relieve pressure points, preventing pressure sores, etc. Most memory foam has the same basic chemical composition, however the density and layer thickness of the foam means different mattresses feel very different. A high-density mattress will have better compression ratings over the life of the bedding. The lower density will suffer from slightly shorter life due to the compression that takes place after repeated use.