Who invented the fluorescent lamp?

According to the U.S. Department of Energy, engineer and inventor Peter Cooper Hewitt created the first usable fluorescent lamp in the early 1900s. While earlier inventors and researchers experimented with fluorescence, Hewitt's design led to the first commercially successful form of fluorescent lighting.

These early lamps created light by allowing electricity to pass through mercury vapors in a glass tube. The bulbs also produced a bluish green light. The later addition of phosphor coating applied to the glass created the more recognizable white hue of modern fluorescent lamps. Fluorescent light bulbs use up to 75 percent less energy than incandescent lights and last up to 10 times longer.