The principle of burning limestone to produce light was discovered in 1825 by a Scotsman named Thomas Drummond. Limelight is created by heating a block of quicklime using a mixture of oxygen and hydrogen. This produces an intense white light, which, when projected from a lantern with a reflector and lens, is highly directional.
Limelight was first used in 1837 for the pantomime season at Covent Garden in London, England. It was generally used for effects or following performers around the stage. Because the quicklime block needed to be adjusted constantly to maintain an even beam from the limelight, each one required an operator.
Limelights were replaced with electric arc lamps as follow spots in the early 20th century, although their legacy remains. Follow spots and their operators are still sometimes referred to as "limes" in theaters, and the phrase "in the limelight" refers to their use to highlight a particular person onstage.