This is a new type of foam, the technical term for which is Visco Elastic. It has its own individual feel and moulds to your body using your weight and temperature. It therefore follows the shape of the user and reverts to its original shape when the weight and pressure is removed. It has good pressure relieving properties, is hypoallergenic and is available in a variety of qualities and depths. Different feels, or firmness, can be achieved by altering the thickness and density of the Visco elastic used. Manufacturers also use Visco elastic as a filling to put on top of a spring unit but this will be a much thinner layer and will give a different feel to those mattresses that do not contain any springs. Memory Foam mattresses have the added advantage of not needing to be turned. The latest memory mattresses have cool gel on the top of the mattresses to alleviate any heat issues.