Beer is the world's most widely consumed alcoholic beverage, dating back thousands of years to ancient Egyptians and Mesopotamians. It is made from four key ingredients - water, barley, hops, and yeast - and comes in various colors and flavors depending on the brewing technique used, such as lagers which are cold-fermented. Beer has played an important economic and political role throughout history, sometimes used as currency by ancient Egyptians and with a powerful lobbying presence in modern US politics.