Biological aging is a special form of aging wine. Once alcoholic fermentation has finished, and under special conditions, yeasts in wine can spontaneously form a biofilm called flor on the surface of the aging wine. This flor essentially consumes oxygen in the wine yet protects it from oxygen in the air. This leads to various new aromas and flavors in the finished wine. Fino sherry is the most prevalent example of such wines and clearly shows fresh, doughy flavors that emerge from aging under flor. (Wine/Production)