A baker adds yeast to a mixture of flour, water, and sugar for a very different reason, but the yeast does exactly the same thing–it changes the sugar into alcohol and carbon dioxide. The carbon dioxide fills the dough with gas, making it rise. The alcohol then evaporates during baking. For the vintner, the yeast produces alcohol while the by-product is carbon dioxide. For the baker, the yeast produces carbon dioxide to make the bread rise, and produces alcohol as a by-product. In short, the baker’s by-product is the vintner’s key ingredient, and the vintner’s by-product is what makes the baker’s bread rise. If you cap the bottle before the yeast has finished, you can keep the carbon dioxide and the alcohol. The result is champagne.