This Sheet Set features Outlast technology. Outlast? technology, originally developed for NASA, utilizes phase change materials (PCM) that absorb, store and release heat for optimal thermal comfort. Outlast? technology is comparable to ice in a drink; as it changes from solid to liquid, it absorbs heat and cools the drink, keeping that drink at the desired temperature for longer. Outlast? technology is not wicking technology, which manages moisture by reacting to your sweat and pulling it away from the skin. Outlast? technology will proactively manage heat while controlling the production of moisture before it begins.