An incandescent lamp is a type of light bulb that produces light by heating a thin wire until it glows white-hot. Inside the glass bulb, electricity flows through a coiled wire called a filament, usually made of tungsten metal. The electricity makes the filament so hot (around 4,500 degrees Fahrenheit) that it glows brightly, filling the room with light.

Thomas Edison perfected the incandescent lamp in 1879, though he wasn't the only inventor working on the problem. His key insight was finding the right filament material and removing most of the air from inside the bulb so the filament wouldn't burn up immediately. Before electric incandescent lamps, people relied on candles, oil lamps, and gaslight, which were dimmer, smokier, and more dangerous.

For over a century, incandescent lamps were the standard way to light homes, schools, and offices. You could recognize them by their warm, yellowish glow and the way they got hot to the touch after being on for a while. Today, most incandescent bulbs have been replaced by LED and fluorescent lights, which use far less electricity to produce the same amount of light. But incandescent lamps remain important in history as the technology that transformed how humans live after dark.