In 1899 Farbenfabriken vormals Friedrich Bayer & Co. (later Bayer AG) introduced aspirin, a pain-reliever that would come to rank high among the world’s most commonly used drugs. The company credits the synthesis of pure acetylsalicylic acid, aspirin’s active ingredient, to Bayer chemist Felix Hoffmann. However, decades after its introduction, former Bayer chemist Arthur Eichengrün cried foul, claiming to have invented the process of the compound’s synthesis himself, with Hoffmann merely carrying out the procedure. Bayer holds by its claim that Hoffmann was the inventor.