The glass on the left is young, smells like ripe berries, and when you take a sip it fills your mouth with tart bitterness. You swallow, and your mouth feels dry and slightly chalky. The glass on your right smells like earth and leather. The fruitiness is still there, but its taste is more subtle, and mixed with chocolate, licorice, and leather. You swallow, and your mouth feels fuzzy and warm. The flavors taper off slowly.
Even if you are a novice wine-taster, a properly aged wine will taste and feel very different from the younger version. Why is it that some wines taste better as they get older while others get worse? And perhaps most important, how in the world do you tell them apart before it's too late?
A bottle of wine might look like a closed system, but inside there are complex chemical transformations that scientists are still unraveling.