Almost all beers today, from the snob’s favorite quadruple IPA to the cheap beer in your morning-after michelada, have one little green herb in common: hops. The pinecone-like bud of the climbing humulus lupulus plant flavors every beer on Earth. (It’s also a cousin to cannabis.) Brew without it, and it’s not technically considered beer, but a food product regulated by the FDA. It’s hard to even think about consuming craft beers without it, but ancient brewers used to flavor their wares with whatever they could find.
http://munchies.vice.com/articles/how-to-drink-hallucinogenic-beer-like-a-viking-shaman