Hops are the flowers of the Humulus lupulus or hop plant. The plant grows very quickly and easily reaches a height of 20 feet each growing season. Beer enthusiasts have been keen to increase the agricultural understanding of farming brew hops.  However, hops have only been the subject of medical research in the past few centuries. The first known references to the use of hops for brewing beer are from Germany and France early in the 9th cenuty. Obviously, brewers used hops for generations before. These are only two references in documents that we happen to have for beer recipes using hops. Brewing Hops and Brewing Beer The Hops do not supply any alcohol content to the beer when it is brewed. Instead, brewing hops help balance the bitterness of the malt and provide more fruity or citrus flavours to the beer when brewing. There are approximately 80 different varieties of hops that are used for commercial brewing of beer in the world. Commercial brewers divide and classify hops under three categories: bittering hops, dual purpose hops and aroma hops. The categories are based on whether they tend toward more bitter or fruity flavors. The earliest and most important research into hops examined the medicinal properties of hops because of its often observed effect and ability to induce sleep. The French pharmacist, Planche identified Lupulin, which is a very fine yellowish resin from the female flowers of hops, as the source of the sedative effects in 1813.  Other health benefits of hops include aiding females during menopause. You can learn more about hops from the American Botanical Council here. Slovenia has a whole research institute devoted to reseach on hops, which you can find here.