The light bulb (incandescent lamp) is like the ones used at home. The enclosure of the lamp is a bulb made of thin glass. Inside the glass are inert gases such as nitrogen and argon. In the centre there is a very thin wire (called filament) made of tungsten. Tungsten is a metal that melts at an extremely high temperature. When electricity passes through the wire, it becomes warm. As the temperature increases, the wire almost melts and it then starts illuminating like all hot metals do. This illumination is the light.