The Babylonians and Romans developed oil-based lamps, but that technology virtually disappeared during the (appropriately named) Dark Ages. For almost two thousand years, all the way to the dawn of the industrial age, the candle was the reigning solution for indoor lighting. Candles made from beeswax were highly prized but too expensive for anyone but the clergy or the aristocracy. Most people made do with tallow candles, which burned animal fat to produce a tolerable flicker, accompanied by a foul odor and thick smoke.
