Hyaluronic acid: Hyaluronic acid is found in all living organisms and is a commonly found component of human tissue. hyaluronic acid was first isolated and extracted from the vitreous humor of the bull’s eye in 1934. In the last 20 years, hyaluronic acid has been widely used in cosmetic and therapeutic applications, including the treatment of joint pain and tissue fillers. Hyaluronic acid is a macromolecule formed by the polymerization of multiple repeating disaccharide units (including glucuronide and N-acetylglucosamine). Only two sugar units, glucuronide and N-acetylglucosamine, are present in hyaluronic acid. Different species of hyaluronic acid all have the same molecular structure. Hyaluronic acid has very good biocompatibility, which means that hyaluronic acid is an ideal material for medical use.