The key ingredient in Slumber Cloud bedding is Outlast technology. This is made from Phase Change Materials (PCMs) - microscopic wax-like capsules that absorb, store and release heat. These PCMs are integrated into polyester or other synthetic fabric blends to create a temperature buffering effect. Additional layers may be made from Celliant, Tencel, antimicrobial silver and other advanced performance fabrics. So Slumber Cloud consists of a high-tech blend of fabrics for dynamic temperature regulation. The Outlast PCMs provide the core heat absorbing and releasing technology.