Aspirin (acetylsalicylic acid) is a novel organic compound that does not occur in nature, and was first successfully synthesised in 1899. In 1897, scientists at the drug and dye firm Bayer began investigating acetylated organic compounds as possible new medicines, following the success of acetanilide ten years earlier. By 1899, Bayer created acetylsalicylic acid and named the drug 'Aspirin', going on to sell it around the world.:27 The word Aspirin was Bayer's brand name, rather than the generic name of the drug; however, Bayer's rights to the trademark were lost or sold in many countries. Aspirin's popularity grew over the first half of the twentieth century, leading to fierce competition with the proliferation of aspirin brands and products.Aspirin's popularity declined after the development of acetaminophen/paracetamol in 1956 and ibuprofen in 1962. In the 1960s and 1970s, John Vane and others discovered the basic mechanism of aspirin's effects,:226231 while clinical trials and other studies from the 1960s to the 1980s established aspirin's efficacy as an anti-clotting agent that reduces the risk of clotting diseases.:247257 Aspirin sales revived considerably in the last decades of the twentieth century, and remain strong in the twenty-first with widespread use as a preventive treatment for heart attacks and strokes.:267269

Felix Hoffmann (21 January 1868 – 8 February 1946) was a German chemist notable for re-synthesising diamorphine (independently from C.R. Alder Wright who synthesized it 23 years earlier), which was popularized under the Bayer trade name of "heroin". He is also credited with synthesizing aspirin, though whether he did this under his own initiative or under the instruction of Arthur Eichengrün is contested.