Mycelium is the vegetative portion of a fungus. It consists of a web of hyphae, branching or forking thread-like structures. Depending upon the type of fungus, and how well developed it is, mycelia may be visible or microscopic. The mold that grows on decaying food, for example, is a visible form. In addition to asexual reproduction, the mycelium is responsible for absorbing nutrients from the environment. It releases enzymes into the surrounding environment to break down the food source into a digestible form, then absorbs it. This process also helps dead plant material and other organic material to decompose. The material can also help renew the soil through this process, for example by decomposing contaminants such as pesticides. Some mycelia help plants absorb water and nutrients more efficiently, and others are also important food sources for invertebrates living in the soil. In the picture above, mushrooms have mycelium, but they are usually on a microscopic level, so you can’t really see them.