Memory foam mattress does not contain springs or any other materials that are traditionaly used in mattress making. They contain a thick viscoelastic foam, called memory foam, that gives way when you press on it and slowly returns to its original shape when you remove the force. Memory foam was invented by NASA back in 1970’s for aircraft safety reasons and it was industrialized in the 80’s mainly because of its ability to take the shape of the object that applies force on it. This mattress can perfectly react to your movements and it’s temperature sensitive so expect it to sink more as your body temperature warms it up. It’s not recommended to people with very high body mass index (>30) since their weight may force the mattress to sink making it uncomfortable.