Every autumn a microscopic fungus called le « Botrytis Cinerea » appears and transforms the grapes. This is the famous 'noble rot' that is Nature's gift to Chateau Guiraud. In autumn the grapes take on a dark colour which can even seem austere, but this 'noble rot' is a precursor of aromatic expression. Understanding this phenomenon is essential as only the grapes that have been perfectly concentrated by the Botrytis will be picked one by one.