Mycorrhizae is a symbiotic relationship between beneficial fungi and plants. Mycorrhizal fungi live in and around the roots of most plants. In exchange for sugars and simple carbohydrates, the mycorrhizal fungi absorb and pass on minerals and moisture required for the plant's growth. Over tens of millions of years plants have developed a symbiotic relationship with the fungus to help them survive conditions of drought, extreme temperatures and periods of low soil fertility. Mycorrhizal fungi colonize a plant's living root system, in effect extending the root system further into the soil - sometimes by up to 1000%! By taking in nutrients and water and passing it on the roots, these organisms are a vital link in a plant's nutrient cycle. In nature, mycorrhizal fungi are found on about 99% of plant species, but in urban environments, the poor, compacted soils often lack this essential fungi.