A: Tannins are a kind of flavonoid that occurs naturally in everything from berries to red beans to nuts, although we associate them particularly with red wines. Have you ever taken a sip of red wine and felt as though your mouth had turned into a cartoon of the Mojave desert? Tannins are the culprit. Found on the skin of grapes, as well as in the seeds (known as pips) and stems, tannins can create that sensation of dryness in your mouth, but they also add a mild bitterness to red wines which we generally find pleasant. Tannins are responsible for increasing a wine’s complexity; they extend its finish, and can help preserve it by preventing oxidation. Tannins generally get milder with age and can lend a velvety richness to older wines.