Methylsulfonylmethane (MSM) is an organic sulfur compound that is a white, odorless, crystal, appearing similar to sugar and is noted for its exceptionally non-toxic nature. By weight, MSM is 34 percent bio-available sulfur, making it one of nature's richest sources of sulfur. Sulfur is the eighth-most abundant substance in body by weight. Elemental sulfur is present in every cell and is structurally and functionally important in more than 150 compounds in the body including tissues, enzymes, hormones, antibodies and antioxidants. In animals, the highest concentration of sulfur is found in the joints, hair, skin and nails.