What is the function of leavening agent?

The function of leavening agents is to cause the baked goods (breads, cakes, etc.) to rise. There are different types of leavening agents, such as yeast, baking powder and baking soda. Eggs are also sometimes used as a leavening agent, especially in some pound cake recipes. Without leavening, the baked goods will not only be flat, but won't taste as good, either.