Baking powder is a white powder used in baking that makes cakes, muffins, and biscuits rise and become fluffy instead of staying flat and dense. When you mix baking powder with wet ingredients and heat it in the oven, it releases tiny bubbles of carbon dioxide gas that get trapped in the batter, creating air pockets that make baked goods light and tender.

Before baking powder was invented in the 1850s, bakers had to use yeast, which requires hours of waiting for dough to rise, or they had to carefully mix baking soda with acidic ingredients like buttermilk or vinegar. Baking powder changed everything because it contains both the base (baking soda) and the acid already mixed together, along with a starch to keep them from reacting until you're ready. This means you can quickly whip up a batch of pancakes or muffins on a Saturday morning without waiting around.

Most baking powder is double-acting, meaning it releases some gas when mixed with liquid and then releases more when heated. If you forget the baking powder in a recipe, your cookies or cake will turn out disappointingly flat and heavy. Just a teaspoon or two makes an enormous difference in how your baked creations turn out.