The qualities of hydrogels, water swollen, three dimensional networks of crosslinked hydrophilic macromolecules, are explored in this article. The origin, structure and behavior of gelatine, agar, and carrageenan, all of which are natural hydrogels, are summarized. Information on gelling temperatures, concentrations, and relative rigidities of the dried films is included. Industrially, interest in the absorbent qualities of hydrogels is developing. However, some of the properties which affect their absorbency are of equal importance in determining their behavior as adhesives, sizes, and fixatives. -- AATA