Yeast is a living microorganism commonly used as a leavening agent in baking and brewing, known for producing carbon dioxide and alcohol through fermentation. It imparts a subtle, earthy flavor to baked goods and has a light, airy texture when dough rises. Widely utilized in international cuisines, yeast is essential for making bread, beer, wine, and various fermented foods across cultures. Historically, yeast has played a crucial role in food preservation and the development of traditional bread and beverage recipes around the world.