Muscle FuelLean MassCreatine is a compound that occurs naturally in the body, primarily in skeletal muscle. Creatine’s function is to serve as a precursor to adenosine triphosphate (ATP), the form of chemical energy used by all cells. Body stores of creatine create a pool of readily available ATP for energy, which is necessary for fueling quick bursts of power and strength. Studies have demonstrated that creatine supplementation can help to maintain existing muscle tissue, support the growth and development of lean mass, and promote optimal performance during short bouts of intense exercise. NOW Creatine Monohydrate has no additives or preservatives.