If the United States had a national alcoholic beverage, then it would be beer. In 2011, the total beer market in America was $96 billion and about 200 million barrels of beer were sold (1 barrel of beer = 31 gallons). Also,1,989 US breweries fermented everything from mild beer to chocolaty liquor in the same year.

What's inside a glass of beer?

It's mostly water. But it also has flowers, grains and fungus. Beer acquires most of its taste from hops, the flowers that seem like mini-pinecones. The beer's alcohol content comes from grain, typically barley, that is malted (or germinated) and steeped in water to get its sugars. Such sugars attract yeast, that unicellular fungi thriving on sugars and excreting alcohol. 

Before beers get bottled, yeasts are filtered out, although they leave some traces (and tastes) behind. A study by the Journal of Proteome Research discovered that beer contains 62 different proteins and 40 of them come from yeast. 

Why do the bubbles float down?

You may notice that when you pour the beer into a glass, some bubbles float down and not up. Due to the drag from the glass walls, the bubbles float up much easier in the middle of the glass. When these bubbles go upward, they tend to pull the liquid to the surface. Once the bubbles come into contact with the beer's froth, the liquid starts to pour back down the glass' sides, pulling down smaller bubbles with it.