Also called aging en tirage, it is the aging of champagne in the bottle before disgorgement. By the end of the second in-bottle fermentation, the yeasts have transformed the sugars into alcohol and carbon dioxide. The yeasts then gradually die and decompose becoming lees in a process known as autolysis, contributing to the typical and much appreciated yeasty aromas of champagne. Slow oxidation of the wine will also occur as the crown stopper (or cork) allows minute quantities of oxygen to enter the bottle. The prolonged contact with the lees during the aging keeps the wine fresher than if it had been disgorged (and the lees removed).