Hops are the female flowers (also called seed cones or strobiles) of a hop species, Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine. In the Middle Ages beers tended to be of a very low alcohol content and were commonly consumed as a safer alternative to untreated water.