Silicones, like plastics, were invented in the 20th century and have since become a colourful, omnipresent part of our lives. Silicones are made of repeating units of siloxanes: silicon-oxygen chains. In their many forms - oils, gels, foams and solids -they are valuable in electronics, medicine, transport and other industries; significantly, their unique sets of properties help improve energy efficiency and reduce waste (they tend to be very light and durable, and make excellent thermal insulators and lubricants).