Hydrogel polymers are hydrophilic resins that display excellent biocompatibility, which has allowed their application in diverse fields of surgery and medicine. The original hydrogel polymer, a copolymer of 2-hydroxyethyl methacrylate and ethylene dimethacrylate, was developed by Wichterle and Lim in 1954. The development of the first soft hydrogel contact lenses by Wichterle in 1961 represented the first successful clinical application of hydrogel polymers and remains one of the most important uses of hydrogels today. The biocompatibility of hydrogel polymers may be adapted to diverse tissue types by small variations in the makeup of the polymer, including varying the type and amount of monomers and differing the amounts and characteristics of the cross-linking agents used to create the polymer chains. Hydrogels have been successfully developed for use as coatings, soft contact lenses, wound dressings, and drug delivery systems.