Original: Champagne is a single Appellation d'Origine ContrÃ lÃ e/O. As a general rule, grapes used must be the white Chardonnay, or the dark-skinned "red wine grapes" Pinot Noir or Pinot Meunier.
Simplified: They can be made from white Chardonnay grapes, or red Pinot Noir or Pinot Meunier grapes.