Mycelium is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. Mycelia are vital in terrestrial and aquatic ecosystems for their role in the decomposition of plant material. They contribute to the organic fraction of soil, and their growth releases carbon dioxide back into the atmosphere. Mycelium is also an important food source for many soil invertebrates and is vital to agriculture, being important to almost all species of plants, many species co-evolving with the fungi. Networks of mycelia can transport water and spikes of electrical potential. Mycelium is a part of a mushroom that is very similar to the root system of any plant. It is a rich network of thin filaments called hyphae that collect food, water, and nutrients to nourish the fungus. It also provides the mushroom with support and anchorage.