The magic of bread happens before it hits the oven. To rise properly, the dough needs plenty of carbon dioxide, which comes from yeast. Those single-celled organisms process glucose and turn it into carbon dioxide (plus a little ethanol). But wheat flour doesn’t naturally contain much glucose. What it does have are starches, which are just long chains of sugar molecules. To get those starches to break down into smaller sugars, you add water to the flour in order to activate the enzyme amylase. Amylase produces maltose, and an enzyme in the yeast breaks down the maltose into glucose. And voila, once you provide a moist, warm environment for the yeast cells, they bubble out all the carbon dioxide you could desire. Kneading the dough will ensure that the yeast—and therefore the bubbles—are evenly dispersed for a consistent texture.