Hops are the female flower cones, also known as strobiles, of the hop plant (Humulus lupulus). They are used primarily as a flavoring and stability agent in beer, though hops are also used for various purposes in other beverages and herbal medicine. The first documented use in beer is from the eleventh century. Hops are used extensively in brewing today for their many purported benefits, including balancing the sweetness of the malt with bitterness, contributing a variety of desirable flavors and aromas, and having an antibiotic effect that favors the activity of brewer's yeast over less desirable microorganisms. The hop plant is a vigorous climbing herbaceous perennial, usually grown up strings in a field called a hopfield, hop garden or hop yard when grown commercially. Many different varieties of hops are grown by farmers all around the world, with different types being used for particular styles of beer.