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It is a synthetic material that is a registered trademark of the German company Basf. It is made from a polymer – a set of successive clusters of molecules – of the chemical compound styrene, expanded into small hollow bubbles from 0.4 to 2.5 millimeters in diameter. This composition is even implied in the other name of the product: polystyrene foam (polymer + styrene). There is, however, a difference: these bubbles make Styrofoam 30 times lighter than common polystyrene. Its expansion is caused by the action of a chemical agent called pentane, which increases up to 50 times the initial size by releasing vapors. More than 97% of the volume of styrofoam is made up of air, which gives the material the property of thermal insulation. The name of the product in English, styrofoam, is also a registered trademark, but of the American company Dow Chemical, which introduced it in the market in 1954, after it was invented by the chemist Ray McIntire.