Balsamic vinegar is a dark, concentrated, intensely flavored vinegar made wholly or partially from grape must: freshly crushed grape juice with all the skins, seeds, and stems. Only two consortia produce true traditional balsamic vinegar, that of Modena and neighboring Reggio Emilia. True balsamic vinegar is made from a reduction of pressed Trebbiano and Lambrusco grapes.

Source: Wikipedia