In the late 19th century, three brilliant inventors, Thomas Edison, Nikola Tesla and George Westinghouse, battled over which electricity system—direct current (DC) or alternating current (AC)–would become standard. During their bitter dispute, dubbed the War of the Currents, Edison championed the direct-current system, in which electrical current flows steadily in one direction, while Tesla and Westinghouse promoted the alternating-current system, in which the current’s flow constantly alternates.