Polyacrylamide gels were introduced in 1959 by Raymond and Weintraub, as supports for electrophoretic separations. The polyacrylamide gel is produced by polymerising acrylamide, with N,N-methylenebisacrylamide or ethylene diacrylate as the cross-linking component. Catalytic redox systems, which yield free radicals, are used to initate copolymerisation (e.g. ammonium peroxydisulphate and N, N, N´, N´-tetramethylethylene diamine). Electrophoresis on polyacrylamide gels is now in general use as a laboratory technique. Its popularity owes much to the transparency of the gel, its mechanical stability and inertness, its stability over a very wide range of pH and its insolubility in most of the solvents commonly used for electrophoresis. The gels can be prepared reliably and reproducibly from analytically pure starting materials, and possesses the decisive advantage that by varying the proportions of the starting materials, gels of different density and pore diameter can be prepared. Various other substances can also be copolymerised into these gels.