More then 20,000 brands of beer are brewed in 180 styles, from ales, lagers and stouts to bitters, cream ales and iced beers. Beer has been a popular beverage for a long time. Babylonian clay tablets show detailed recipes of beer making in 4300 BC. Beer was also brewed by the ancient Chinese, Assyrians and Incas. An Egyptian text of 1600 BC gives 100 medical prescriptions using beer. Commercial beer making was established in 1200 AD in present-day Germany. In 1506, the German Purity Law is issued, specifying that beer ingredients must only be water, barley, wheat and hops. Bottling of beer started in 1605. Brewing is the process of changing water and grain into beer through a yeast catalyst. The quality of the water is extremely important. Hard water produce a bitter ale, soft water produce bitter lager. Barley or hops, or a combination of them, is used for the grain. Getting dry grain ready for fermentation is called malting. The grain is steeped in water until it sprouts. The sprouting or germination is not allowed to end naturally but is interrupted either by drying or roasting in kilns.