In 1839 Polystyrene was discovered, but was only made practical in 1938. In 1954 Styrofoam, the trademarked form of Polystyrene foam insulation, was invented.
Expanded polystyrene is made from expandable polystyrene, which is a rigid cellular plastic containing an expansion agent. EPS is obtained from oil and the raw material for EPS is produced in the form of small polystyrene beads containing a blowing agent, or pentane, which when exposed to steam, expand to form a light weight “pre-foam” of required density. This pre-foam is then processed by further steam treatment until the beads fuse together, either in a mould to give that material a required shape and size or as large blocks for cutting into sheets and shapes.