It is a viscoelastic, temperature sensitive material, quite different from ordinary foam. Viscoelastic describes the property of a substance to both resist flow or change of shape (viscous) and to return to its original shape after being forced to change (elastic). An imperfect version of TEMPUR material was developed for NASA in the 1970s, designed specifically to conform to any individual’s body and relieve the pressure of the tremendous forces of gravity the astronauts experienced during lift off and flight. Like so many NASA technologies, the formula was eventually released to the public. In 1991, Tempur World introduced TEMPUR pressure relieving material, a vastly improved reinvention of the original NASA formula for home and medical use.