With the discovery of fire, the earliest form of artificial lighting used to illuminate an area were campfires or torches. Prehistoric people used primitive oil (animal or vegetable fats) lamps to illuminate surroundings. Fireflies have been used as lighting sources. Candles and glass and pottery lamps were invented. A major reduction in the cost of lighting occurred with the discovery of whale oil, then kerosene was discovered. Gas lighting was economical enough to power street lights in major cities starting in the early 1800s, and was also used in some commercial buildings and in the homes of wealthy people. The next major drop in price came about in the 1880s with the introduction of electric lighting in the form of arc lights for large space and street lighting followed on by incandescent light bulb based utilities for indoor and outdoor lighting. No artist credited.