Sur lie is French for “on the lees,” and lees for their part are expired yeast cells. After yeasts consume grape sugars and turn them into alcohol, the expired yeast cells begin to break down, ultimately settling at the bottom of the fermentation vessel. While the process is complex, wines left in contact with the lees ultimately take on a creamier, rounder mouthfeel. Many well-known wines are left in contact with the lees for a period ranging from weeks to many months. These include most California chardonnays and white Burgundies in addition to many Champagnes.