Nikola Tesla (10 July 1856 – 7 January 1943) was an inventor, mechanical engineer, and electrical engineer. He was an important contributor to the birth of commercial electricity, and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries. Tesla's patents and theoretical work formed the basis of modern alternating current (AC) electric power systems, including the polyphase system of electrical distribution and the AC motor. This work helped usher in the Second Industrial Revolution. Born an ethnic Serb in the village of Smiljan (now part of Gospic), in the Croatian Military Frontier[1] of the Austrian Empire (modern-day Croatia), Tesla was a subject of the Austrian Empire by birth and later became an American citizen.[2] Because of his 1894 demonstration of wireless communication through radio[citation needed] and as the eventual victor in the "War of Currents", he was widely respected as one of the greatest electrical engineers who worked in America.[3] He pioneered modern electrical engineering and many of his discoveries were of groundbreaking importance. In the United States during this time, Tesla's fame rivaled that of any other inventor or scientist in history or popular culture.[4] Tesla demonstrated wireless energy transfer to power electronic devices as early as 1893[citation needed], and aspired to intercontinental wireless transmission of industrial power in his unfinished Wardenclyffe Tower project. Because of his eccentric personality and his seemingly unbelievable and sometimes bizarre claims about possible scientific and technological developments, Tesla was ultimately ostracized and regarded as a mad scientist by many late in his life.[5] Tesla died with little money at the age of 86 in a hotel suite in New York City.[6] The SI unit measuring magnetic field B (also referred to as the magnetic flux density and magnetic induction), the tesla, was named in his honor (at the CGPM, Paris, 1960).