Basically, mattresses are made up of three layers: the support and comfort layers, plus a cover. The support layer consists of innersprings or foam—or a combo of both called a hybrid. Comfort layers are located just beneath the mattress surface. Materials for these layers vary widely and can include memory foam, latex, cooling gel memory foam, cotton, wool and silk. Covers enhance breathability and provide temperature regulation for cooler sleep while offering protection for materials inside the bed. They also increase durability.