A light bulb is used for seeing in the dark.
Incandescent light bulbs use a tungsten filament sealed inside a glass bulb.
Tungsten filament sealed in a glass bulb is used for seeing in the dark.
Tungsten filaments sealed in a glass bulb are used for what in the dark?

* photons
* energy
* seeing
* stay warm
* sleeping
* talking
* communicating
* heat