Mycorrhiza is an association between fungi and roots of higher plants. This association is mutualistic, meaning both the fungus and the plant benefit from it. The fungus colonizes the roots of the plant and forms a network of filaments that extend into the soil. These filaments help the plant to absorb water and nutrients from the soil that it would not be able to access on its own. In return, the fungus receives sugars and other organic compounds from the plant, which it uses as a source of energy. This association is essential for the growth and survival of many plant species, especially those that live in nutrient-poor soils.