The most expensive wines made from Riesling are late harvest dessert wines, produced by letting the grapes hang on the vines well past normal picking time. Through evaporation caused by the fungus Botrytis cinerea ("noble rot") or by freezing, as in the case of ice wine (in German, Eiswein), water is removed and the resulting wine is felt to offer richer layers on the palate. These concentrated wines have more sugar (in extreme cases hundreds of grams per litre), more acid (to give balance to the sugar), more flavour, and more complexity.