Fungi are eukaryotic organisms that can be unicellular or multicellular. They are divided into three main groups: mushrooms, molds, and yeasts. Mushrooms and molds are multicellular and feed on organic matter in damp, shady environments. They reproduce through spores. Yeasts are unicellular and feed on sugars, reproducing through budding. Fungi have important relationships with humans, as they are used to make foods like bread and beer and medicines like penicillin.