The single-celled fungus which makes bread rise is called Saccharomyces cerevisiae, also known as baker's yeast. This fungus is widely used in baking and brewing industries as it ferments sugar and produces carbon dioxide gas, which causes dough or batter to rise. The use of baker's yeast dates back to ancient Egypt, where it was used to make bread. Today, it is still a crucial ingredient in many baked goods and is also used in the production of beer, wine, and other fermented beverages.