Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound, and is best known as the alcohol found in alcoholic beverages. In common usage, it is often referred to simply as alcohol. Its molecular formula is variously represented as EtOH, CH3CH2OH, C2H5OH or as its empirical formula C2H6O (which it shares with dimethyl ether). After the use of fire, fermentation of sugar into ethanol is perhaps the earliest organic reaction known to humanity, and the intoxicating effects of ethanol consumption have certainly been known since ancient times. In modern times ethanol intended for industrial use has also been produced from byproducts of petroleum refining. Because of ethanol's ease of production and its low toxicity, it finds widespread use as a solvent for substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry it is both an essential solvent and a fundamental feedstock for the synthesis of other products. Because it burns cleanly, ethanol has a long history as a fuel, including as a fuel for internal combustion engines.