Acrylamide or acrylamide monomer is the trivial name for propenamide, a water-soluble solid that is highly toxic and irritant, and readily polymerizes under the action of UV light or chemical catalysts into polyacrylamide (Oxford 2006). Polyacrylamide gel is prepared by mixing a monomer (acrylamide) with a cross-linking agent (N,N′-methylenebisacrylamide) in the presence of a polymerizing agent. An insoluble three-dimensional network of monomer chains is formed. In water, the network becomes hydrated. Depending upon the relative proportions of the ingredients, it is possible to prepare gels with different pore sizes. The gels can then be used to separate biological molecules like proteins of a given range of sizes (King et al. 2006). See ‘gel electrophoresis’.