Yeast is derived from small living organisms that are activated when the dough is at rest. As long as there is air in the dough, they nourish one another and produce carbon dioxide. When the oxy­gen is depleted, they fall back on the sugar to transform it into ethanol and more carbon dioxide. The purpose of water is to encourage their work, which leads the dough to double, even triple in volume. The gluten contained in the flour involves its sticky properties by creating a practically airtight barrier. The salt then amplifies the gas-holding capacity, avoiding the formation of excessively large cells. Once cooked, the bread loses its elasticity, the “jam holes” are set, the ethanol is destroyed by the cooking as well as the valiant yeast. A generous, steaming bread remains, as full of holes as a starry sky.