Fungi are eukaryotic organisms that typically consist of a single cell or a multicellular body. They are found in a variety of habitats, including soil, water, plants, and animals. Fungi can be classified into four groups: mold, yeast, mushrooms, and lichen. Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are often found in damp or humid environments, and they can grow on a variety of surfaces, including wood, paper, and food. Some molds can produce toxins that can cause respiratory illness in humans. Yeast are single-celled fungi that reproduce by budding. Yeast are used to make bread, beer, and wine. They can also cause infections in humans, such as vaginal thrush and oral candidiasis. Mushrooms are fungi that generally have a stalk and a cap. Mushrooms can be found in forests, grasslands, and gardens. Some mushrooms are edible, while others are poisonous. Lichen are symbiotic relationships between fungi and algae or cyanobacteria.