Perhaps no other group of plants is known better than the plant tribe of grapes. The grape is known more for its ability to transform into wine, than for its desirability as a table grape or a desert grape. Some grapes contain so much sugar inside the skin, that they will not ferment in on the vine after ripening, but will turn into a raisin. The unique aesthetic quality of the grape is the capacity for producing juice. The juice may be used fresh or fermented into famous vines with distinctive aromas and flavors increasing into quality with aging, some lasting for centuries. The Roman wine makers put floating olive oil in the wine bottles to prevent the wine from oxidizing and fermenting further into vinegar.