Hard to believe that Sémillon’s main claim to fame is its propensity to rot, but because of its soft skin Sémillon is prone to Botrytis cinerea (a.k.a. “noble rot”). The “rot” concentrates the acid and sugar in the grape, and the resulting wine can be complex, rich, sweet, and aromatic. In short: pretty damn nice. The best known of this sweet style wine is Sauternes, coming from the Sauternais region of the Graves, near Bordeaux in France.
Sémillon can also make an elegant dry white wine, but since it can be short on acidity, it is often vinified with Sauvignon blanc.