Lichen is a unique organism that forms a partnership between a fungus and a photosynthetic partner, usually an alga or cyanobacterium. This collaboration allows lichen to thrive in various environments, from rocky surfaces to tree bark. The fungus provides structure and protection, while the alga or cyanobacterium produces food through photosynthesis. Lichens come in many shapes and colors, making them fascinating to observe. They play an essential role in ecosystems by breaking down rocks into soil and serving as indicators of air quality. Some common types of lichen include crustose, foliose, and fruticose, each with distinct appearances and habitats.