Bread and wine make fine companions in a picnic basket, but the two have more than that in common. To make either one, the baker or the vintner has to enlist the help of yeast. Yeast isn’t an important ingredient in the final product, but it’s the biological processes of the microscopic yeast organisms that produce the alcohol and make the bread rise. And in both cases, the yeast works by digesting the sugars in the recipe. Even though the final products are very different, the yeast acts in the same way whether in bread or in wine. When a vintner adds yeast to fresh grape juice, the yeast digests the natural sugars in the juice, breaking the sugar into two simpler chemicals: alcohol and carbon dioxide gas. When the carbon dioxide bubbles to the surface, what’s left is wine.