Lightbulb filament

A lightbulb filament is merely a fine thread of tungsten wire which glows hot as current flows through it. An inert gas in the glass bulb prevents the wire oxidisning and burning out. The lightbulb is an excellent example of spontaneous invention - material and electrical knowledge and technology were ripe for several people to come up with the idea around the same time. Joseph Swan and Thomas Edison receive most of the credit.