The filaments used in early light bulbs were made of carbon. However, the carbon filament can not survive for long at temperatures higher than 2,100 ^oC. Carbon vaporizes from the filament at these temperatures, shortening the life of the filament. The bulb gives off only dim light at lower filament temperatures. 

Tungsten filaments offer the best combination of high melting point and low vapor pressure for all known elemental filament materials.  This allows the filament to be heated to higher temperatures and provide brighter light with good longevity. However, even tungsten filaments fail.

Now, let's explore why a light bulb filament burns out. By understanding how tungsten filaments fail, it should be possible to invent even better filaments and light bulbs.