Yeast is a microorganism in the Fungi kingdom. It is a single-celled organism and is found in water, in soil, on the skin of humans and animals, and on the surface of plants. Yeast reproduces asexually through mitosis. There are 1,500 species of yeast.
Yeast is commonly used in baking and to make alcohol. During fermentation, yeast breaks down sugars and carbohydrates and converts them into carbon dioxide and alcohol. This process causes bread to rise, and it can be used to turn fruit juices into wine and grain mash into beer or whiskey.