The ingredient which causes breads to rise is Yeast, a living organism mixed into the dough prior to baking. Yeast is the same organism that produces Alcohol from various mashes. But as levening agents abound naturally, bread can be made Without Yeast, such as with Essene Bread or by a Raisin Starter. Flour is made by Grinding Grain. Bread can be made from non-grain sources too, such as Potato Bread.