Mushrooms are a type of fungus. There are many different kinds of fungi, including molds and crusts, as well as more developed types that have a stalk and a cap. Fungi are distinct from plants because they do not possess chlorophyll, the green pigment that allows plants to manufacture sugar from the sun's energy; they need to absorb their food from the environment in which they live. Fungi use fibers called hyphae (that as a group are referred to as mycelium), to take in food. The mycelium can remain dormant under the ground for many seasons, similar to the roots of plants. Each hypha that is sent out makes its way through earth/wood/plant matter until it reaches the surface. During the organism's specific growing season, the hyphae develop into mature structures capable of reproducing spores. The structure that you normally see above the ground is the part of the mushroom that is producing and dispersing spores. Each spore is a single cell that is capable of sending out a hypha that will develop into a group and form its own mycelium. If the hypha of one spore meets up with the hypha of another, it begins the sexual process of spore prodcution through special spore-producing cells.