Noble Rot - French: pourriture noble; German: Edelfäule; Italian: Muffa nobile, Hungarian: Aszúsodás. Australia: Sticky Wine)
is the benevolent form of a grey fungus, Botrytis cinerea, affecting wine grapes. Infestation by Botrytis requires moist conditions.
If the weather stays wet, the malevolent form, "grey rot," can destroy crops of grapes. Grapes typically become infected with Botrytis when they are ripe.
If they are then exposed to drier conditions and become partially raisined this form of infection brought about by the partial drying process is known as noble rot.
Grapes when picked at a certain point during infestation can produce particularly fine and concentrated sweet wine.
some of the finest Botrytized wines are literally picked berry by berry in successive tries (French for "selections").(Source: Wiki.)