NOVELTY - Gel with a multiple network structure has a rupture stress, measured as (force when the gel breaks under compression)/(original cross-section area), of 1-100 MPa, and contains 10% or more of solvent.    USE - For diapers, sanitary products, slow release agents, civil engineering materials, structural materials, communications materials, soil improvement agents, contact lenses, intraocular lenses, hollow fiber, artificial cartilage, artificial organs, fuel cell materials, battery separators, impact absorption materials and cushions (claimed), including receivers, cables and joints for communications materials; and artificial joints, blood vessels and skin.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a gel with a multiple network structure which has a first network formed by polymerizing and crosslinking one or more monomers, and a second network formed by polymerizing and crosslinking one or more monomers in the first network so that the second network is entangled in the first, where:    (a) the first network has a higher degree of crosslinking than the second;    (b) the polymer entangled in the first network, where the weight ratio of monomers in the first network to monomers in the second network, or the polymer obtained, is 1:2-100;    (c) one or more monomers of the first network and of the second network consist of water-insoluble and water-soluble monomers; or    (d) the gel contains metal ions, and at least one monomer forming the first and second network forms a complex with the metal ions;    (2) a gel where the contraction degree is 20-95%, where 'Contraction degree' is the weight ratio of the gel uniformly swollen in water to the gel uniformly swollen in saline;    (3) a gel with a multiple network structure which has a first network formed by polymerizing and crosslinking one or more monomers, and a second network formed by polymerizing one or more monomers in the first network to form a polymer entangled in the first network, where one or more monomers of the first network and the polymer formed in the first network are formed from water-insoluble and water-soluble monomers; and    (4) a product which uses the gel.