The development of the incandescent electric lightbulb by Thomas Edison changed America. Electric lights made it practical for ordinary families to stay up later, to read, socialize and otherwise conduct their lives.
The flourescent bulb was bulkier but more efficient. Smaller flourescent bulbs have been introduced in recent years.
Light-emitting diodes, or LEDS, have a multitude of computer-related applications because they can be made very small and housed in arrays, requiring relatively little power.