This was originally developed by Nasa for the seats used by astronauts during take off. Since then it has been widely used in hospitals and nursing homes. During recent years it's popularity has really "exploded". Visco Elastic Foam is a man made heat sensitive material. The body temperature of the sleeper heats up the foam which then moulds itself around the sleeper's body contours. This offers the sleeper fantastic support, the correct sleeping alignment and disperses the sleeper''s weight over a larger area reducing pressure points on the shoulders, back and hips. Visco Elastic Foam has been medically proven to help with numerous ailments including back and joint pain, arthritis, circulation problems and sciatica to name but a few. The quality and price will depend on how much foam has been used and also the density of the foam. The higher the density, the more responsive the foam is. Many foam mattresses are anti-allergenic and provide a very different feel than a traditional fibre filled mattress. You can have memory foam on top of reflex foam, open coil springs, continuous coil springs and pocket springs.