Wine is, in the most general sense, fermented grape juice containing 10% to 15% alcohol by volume. Interestingly enough, it's the only alcohol beverage that can make itself: just throw a bunch of grapes in a big ol' container, stomp on them, let the juice sit for a spell, and eventually it turns into wine (lousy wine, but wine nonetheless). If you examine an unwashed grape, you might notice a faint white bloom on its skin—this is the grape's natural (or what is often called "wild") yeast. There are also natural sugars inside the grape called fructose and glucose, and when the grape is crushed the sugars come into contact with the yeast and natural fermentation begins. This is why so many people call wine the only natural alcohol beverage. The art of making palatable wine, however, is a complicated process involving proper grape selection, fermentation, filtering of sediments, aging, and dozens of other procedures learned through traditional and experimental methods.