As you read this, fungi are busy changing the conditions that govern life on Earth, as they have done for more than a billion years. They are eating rock, decomposing other organisms, digesting pollutants, nourishing some plants and killing others, producing food and medicines, and manipulating animal behavior. For creatures that influence the atmosphere, create soil, and cohabitate inside us, fungi are underappreciated.

There are an estimated 3 million species of fungi – about 8 times the number of plant species – yet more than 90% remain undocumented. Few creatures are more essential or more invisible.

Plants only made it out of the water approximately 500 million years ago because they collaborated with fungi. For tens of millions of years landbased plants used fungi as their root systems until the plants evolved their own. More than 90% of plants still depend on symbiotic mycorrhizal fungi in their roots to obtain water and minerals in exchange for plantmade sugars.

Plant / fungi collaboration extends beyond the soil. Hundreds of fungal species can be found living within the leaves and stems of just a single plant. They weave themselves through the gaps between plant cells and help defend the host against disease. This symbiosis is so universal that no plant grown under natural conditions has been found without mutualistic fungi.

Fungi are one of the five Kingdoms within the eukaryotic branch of the tree of life. It’s a diverse group that includes microscopic yeasts, molds, truffles, mushrooms, and exotic species like Armillaria, one of the largest organisms in the world.

Fungi do not photosynthesize. Like animals, they acquire energy by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment.

One defining characteristic of all fungi is the presence of chitin in their cell walls. Chitin is a long chain molecule also found in the exoskeletons of arthropods (insects and crustaceans) and mollusk radulae (a sharp, tongue-like structure used for feeding).

Mushrooms dominate our conception of fungi, but they are only the fruiting bodies where spores are produced – like apples on a tree. Because they aren’t mobile, fungi use spores to disperse themselves.

Mushrooms lure animals into carrying spores to new territory, but they are only one solution among many. The majority of fungi release spores without producing mushrooms at all. Some species discharge spores explosively, harnessing the power of wind and water to spread.

Fungi produce around fifty megatons of spores each year – equivalent to the weight of 500,000 blue whales – making fungal spores the largest source of living particles in the air. We all breathe fungi.

Aside from the single-celled yeasts, which we use to make bread and alcohol, most fungi grow elaborate branching root networks, known as hyphae (pronounced HY fee). The fruit of these filigreed webs, mushrooms and truffles, arise when hyphal strands merge.

Hyphae webs are composed of tiny organic pipes called mycelium, which shuttle water and nutrients through soil. Mycelium collaborates with plants to form underground ecosystems, and in some cases conduct electricity in a process analogous to the pulses that ricochet through animal nerve cells.

Fungi are metabolic wizards. Using cocktails of enzymes and acids, they break down some of the toughest materials on the planet, from wood to solid rock, crude oil, and polyurethane. Their ability to scavenge via chemical transformation is rivaled only by bacteria.

A species of fungus isolated from mining wastes is one of the most radiation-resistant organisms ever discovered. The abandoned Chernobyl nuclear reactor has been found to host a similar population, which are believed to be directly harnessing ambient radiation as a source of energy.

Human cultures have harnessed the chemical virtuosity of fungi for millennia. The aboriginal people of Australia treated wounds with molds harvested from eucalyptus trees. Egyptian papyruses dating back to 1500 BCE refer to the medicinal benefits of mold. The Jewish Talmud features a mold cure called “chamka.”

In 1928 Alexander Fleming discovered a mold that produced a bacteria-killing chemical we now call penicillin. Fungus-derived medicines have been, dare I say it, mushrooming ever since.

There is cyclosporine, an immune suppressant drug that facilitates organ transplants. The anti-cancer compound Taxol is derived from a fungus that lives in yew trees. Cholesterol-fighting statins and a host of anti-viral medicines also originated from fungi. Fully 15% of all vaccines are produced by genetically engineered strains of yeast.

Industrial applications for fungalderived compounds have also flourished. Citric acid, produced by fungi, is used in virtually all fizzy drinks. In fact, 60% of the commercial enzymes used in industry today are generated by or derived from fungi.

Some fungi are poisonous, and others cause diseases in plants and animals. Yet few organisms are as ubiquitous or as crucial to life. Perhaps it is time to give these metabolic marvels their due recognition.