By the young age of 22, Edison had sold his first patent, that of the stock-ticker, which was immediately introduced into use. His uncanny ability to work for days on end with little rest has been well-documented, and his rare combination of inventive genius and business acumen allowed not only inventive, but also commercial success. While his inventions are too numerous to list, of course, among his best known are the light bulb, phonograph, storage battery and film projector. He held more than 1,000 patents at the time of his death.