Creatine is a naturally occurring organic acid that helps to supply energy to all cells in the body. It was identified in 1832 as a component of skeletal muscle, and is produced in the human body from amino acids in the kidney and liver. From there, it travels through the blood for use by our muscles. Our skeletal muscle holds approximately 95% of the human body's total creatine. Creatine's value as an energy source has been understood since the beginning of the 20th century. In 1912, Harvard researchers Otto Folin and Willey Glover Denis discovered proof that ingesting creatine can dramatically boost the creatine content of the muscle. In the late 1920's, scientists also discovered that creatine is a key player in the metabolism of skeletal muscle. It was popularized as a performance-enhancing supplement in 1992, after it was revealed that Linford Christie, the 100-meter gold medal winner, Sally Gunnell, 400-meter hurdles gold medalist, and Colin Jackson, 100-meter gold medalist, had all taken creatine before the Barcelona Olympics. Since then, creatine supplementation has advanced well beyond the Olympics and is often included as part of a workout regimen by athletes and non-athletes alike to help gain muscle mass. It is especially popular among wrestlers, bodybuilders and sprinters.