Fungi have several positive economic effects, such as consuming biodegradable waste, improving soil, acting as symbiotic organisms for various crops, generating antibiotics and other medicines, and being a food source. They also have several negative effects, including causing diseases in humans and animals and blighting crops and other plants, Fungi are an important category of life, both to human economies and to the other forms of life on the planet.
Fungi are ubiquitous, both in nature and in most human structures as well. They are a major decomposer and are thus responsible for rendering dead organic matter into usable forms for other organisms. They are also frequently harmful to humans, whether by destroying stored food, causing diseases such as athlete's foot, damaging structures or killing crops. On the other hand, fungi are not only used as food themselves but help process some alcohols, cheeses and baking.
Fungi can be either unicellular like yeasts or multicellular like edible mushrooms. Multicellular fungi have very diverse habits, but all share a similar basic structure. Their bodies are composed of tiny threads known as hyphae. These threads burrow through organic material and absorb nutrients. A large mat of hyphae is known as a mycelium.