Plastic
In 1907, while trying to develop a synthetic varnish, Leo Hendrik Baekeland blended the resin of two chemicals and heated the mix under pressure. The resulting polymer proved useful not only as a varnish, but also for making billiard balls.
Extensive use of plastics began during World War I, when the use of petroleum – easier to process into resins than coal – became more widespread.
The sheer material demands of the World Wars, and the economic hardships of the Great Depression in between, led to widespread use of plastics as a cheap substitute for other raw materials in a wide variety of consumer goods.
Though negative associations with plastic as a "cheap substitute" persist, that attribute has placed a wider range of consumer goods within the reach of millions more people. It has helped the plastics industry develop new resins, new uses and spawn entire new industries. Today, plastic is used to make everything from pantyhose to prosthetic limbs, from toys to the window frames on the Space Shuttle.