Edison's first job was as a telegraph operator, and in the course of his duties, he redesigned the stock-ticker machine. The Edison Universal Stock Printer gave him the capital ($40,000) to set up a laboratory in Menlo Park, New Jersey, to invent full-time (with many employees).

Edison experimented with thousands of different light bulb filaments to find just the right materials to glow well, be long-lasting, and be inexpensive. In 1879, Edison discovered that a carbon filament in an oxygen-free bulb glowed but did not burn up for quite a while. This incandescent bulb revolutionized the world.

Edison and General Electric fiercely promoted the use of direct current (Westinghouse and Nikola Tesla developed and promoted the use of the more useful alternating current, which eventually became the standard). Edison also invented the alkaline battery.

In 1887, Edison moved his lab to West Orange, New Jersey, and employed about 5,000 people. Altogether, Edison patented 1,093 inventions. Edison was quoted as saying, "Genius is one percent inspiration and 99 percent perspiration." On October 21, 1931, a few days after Edison's death, electric lights in the United States were dimmed for one minute.