Argon, 1894. Discoverers : Sir William Ramsay and Baron Ray Leigh (Great Britain).
Aspirin, 1899. Inventor : Dr. Felix Hoffman, Germany.
Atom Bomb, 1945. Inventor : Julius Robert Oppenheimer (U.S) (1904-1967).
Autogiro, 1923. Inventor : Juan de la Cierva (Spain) (1896-1963). Horizontal unpowered rotor.
Automobile (steam), c. 1769. Inventor : Nicolas Cugnot (France) (1725-1804). Three-wheeled military tractor. Oldest surviving is Italian Bordino (1854) in Turin.
Automobile (gasoline), 1855. Inventor : Karl Benz (Germany) (1844-1929). Earliest model by Father Ferdinand Verbiest (d. 1687) c. 1665 in China. Earliest internal combustion automobile built (1862-63) by Jean Joseph Etienne Lenior (1822-1900) (France). First run by Benz Motorwagon, Manneheim in November or December 1885. Patented in January 29,1886. First powered handcartwith internal combustion engine was by Siegfried Marcus (Austria) (c. 1864).
Bakelite, 1907. Inventor : Lwo H. Backcland (Belgium/U.S.) (1863-1944).
Balloon, 1783. Inventor : Jacques Montgolfier (1755-99) and Joseph Montgolfier (France) (1740-1810). Tethered flight, Paris (October 15); manned free flight, Paris.