The Sémillon grape is rather heavy, with low acidity and an almost oily texture. It has a high yield and wines based on it can age a long time. Along with Sauvignon blanc and Muscadelle, Sémillon is one of only three approved white wine varieties in the Bordeaux region.
The grape is also key to the production of sweet wines such as Sauternes. For the grapes to be used for sweet wine production, they need to have been affected by Botrytis (also known as "Noble Rot"). This fungus dries out the grapes, thus concentrating the sugar and flavours in the grape berry.