Noble Rot

Noble Rot sounds neither noble nor tasty.  However, the term noble rot refers to a microscopic fungus that, under the certain conditions, has the potential to produce liquid ambrosia. 

From Cornell University's fact sheet on noble rot (AKA Botrytis cinera):

"Botrytis blight or gray mold is a fungus disease which infects a wide array of herbaceous annual and perennial plants. There are several species of the fungus Botrytis which can cause blights; the most common is Botrytis cinerea. Botrytis infections are favored by cool, rainy spring and summer weather usually around 15C (60F). Gray mold can be particularly damaging when rainy, drizzly weather continues over several days."

When Botrytis is actually noble it can result in something like Chateau d'Yquem (one of the most expensive wines in the world), which is from Sauternes, a subregion of Bordeaux in France.

Here's how this wine, and similar wines are created
This intense sweetness partially inhibits yeast and fermentation can be very slow, lasting for months. High concentrations of glycerol develop during these extended fermentations and the resulting wines can be fragrantly enticing, exceptionally smooth, and extremely long-lived, cellaring well for decades.

Some grape varietals can be positively affected by Botrytis.  These include Sauvignon Blanc, Semillon and Riesling.  Conditions must be right:  Namely a short period of rain/humidity late in the growing season followed by sunny, cool weather.  When this occurs, the fungus pricks a grape’s skins and takes water from the grape’s flesh.  The grape shrivels and sugars become quite concentrated.

Affected grapes are hand-picked.  Their high sugar levels make fermentation slow, which results in a fragrant, smooth and age-worthy wine.

One traditional and interesting food pairing with Sauternes is foie gras.  This is a classical French appetizer.  Try it sometime.  Personally when I spend a bundle on Sauternes, I drink it very slowly and by itself.

FYI, German Riesling can also be affected by noble rot (Edelfaule in German).  It's usually sold in smaller bottles (375ml or thereabouts) and labeled as 'TBA' or if you're a German enthusiast, 'Trockenbeerenauslese.'