On the bark of the oak tree, a crusty mint colored organism encircles the tree. This mint colored item is a Lichen. What composes a lichen is a mycobiont, and photobiont, a mutualistic symbiotic relationship between two organisms, that results in a composite organism, known as the lichen. The mycobiont is the fungus of a lichen, while the photobiont will be either green algae or cyanobacteria. Commonly, the fungus will provide protection for the photobiont, and in turn this photobiont provides nutrition to its protector. Linchens will often qualify under the fungal kingdom due to fungi being the major partner of the lichen, by systematists. When concerned with the structure of a lichen, once lichen symbiosis is reached, the fungi will greatly influence the body shape of the symbiotic lichen, determining often if it is flexible or tough. Furthermore, the structure of a lichen consists of a cortex (top portion), algal layer (middle layer), and lastly a medulla (bottom portion). Along with these basic layers of a lichen, four various shapes of a lichen exist. They are crustose, squamulose, foliose, fruticose. Crustose is a crust like shape lichen, that is often found on the bark of a tree, or on a rock. While a squamulose shaped linchen are scaly linchens, composed of numerous small rounded lobes. A foliose linchen, is similar to being flat and leaf-like. And finally fruticose, are miniature shrub-like linchens. As can be seen, the symbiotic relationship between mycobiont, and photonion, and the structure of a linchen is perplexed and complicated enough, to be considered a mini-ecosystem. Along with the various shape and structure of a linchen, this composite organism lives in distinct environments. Linchens can be found across an array of various environments, existing in extreme environments like rocky costs, arctic tundra, scorching deserts, to toxic areas. However, linchens are commonly found in mestic habitats. Linchen behavior is characteristically characterized by stagnant, idle growth due to living in areas with small periods of when water is available. However linchens, despite not living in heavy moist climates, continue to live for hundreds of years. Also worth noting about linchens, is their remarkable ability to obtain 3 to 35 times water than their body weight, and gradually drying out, key to surviving in harsh climates. Moreover in concerns to linchens reproductive behavior, a linchen reproduces through asexual reproduction, utilizing either the dispersal of diaspores, or vegetative reproduction. With such a complicated mutualistic symbiotic relationship, linchens have aided in assessing air pollution and other detrimental environmental activities, as linchens are extremely sensitive to environmental disturbance. Additionally, linchens aid in creating dyes, perfumes, and traditional medicines. Consequently, one may conclude, the linchen is an intriguing composite organism, that people have just begun to unlock its potential.