Wines aged sur lie (French for "on the lees") are kept in contact with the dead yeast cells and are not racked or otherwise filtered. This is mainly done for whites, to enrich them (it is a normal part of fermenting red wine, and so is not noted). Originated in Burgundy, with Chardonnay. Popular in Muscadet, Alsace, Germany (Riesling and Pinot Gris) and California. Adds complexity to Chardonnay and Sauvignon Blanc; can occasionally be overdone and lead to a leesy flavour that is off-putting.