Beer is a fermented beverage principally made from four ingredients: water, malted barley, hops, and yeast. Each one of these ingredients will impart its own flavor characteristics to the finished product, one which is almost as old as civilization itself.
One Egyptian recipe called for bread to be left out in the rain and then allowed to ferment. The result was a soggy but mysteriously invigorating concoction.
Here is how it looks under the microscope: