Research on hydrogels has been geared toward biomedical applications from the beginning due to their relatively high biocompatibility. Initially only the hydrophilic nature and the large swelling properties of hydrogels was explored. Continued research on hydrogels has resulted in the development of new types of hydrogels, such as environment-sensitive hydrogels, thermoplastic hydrogels, hydrogel foams, and sol-gel phase-reversible hydrogels. Application of hydrogels ranges from biomedical devices to solute separation. Examples of hydrogel applications in pharmaceutics, biomaterials, and biotechnology are briefly described.