 Have you ever been hiking and seen the beautiful colors that paint the rocks and boulders around you? What you're seeing is called rock lichen and is one of the most fascinating and complex of all living organisms. Lichens are a product of a symbiotic relationship between microscopic algae cells and fungal filaments. Rock lichens come in a variety of bright colors from red, orange, and yellow to brilliant shades of green. There are hundreds of species found in the United States and Wyoming. The lichen body is composed of algae cells living inside a compact mass of fungal tissue. The algae are photosynthetic and provide the fungus with carbohydrate nutrients. Each of these life forms need each other and could not survive on their own. A dozen or more species may grow on a single boulder, often completely covering the rock surface. Rock lichens spend most of their lives in a dormant state and have extremely slow annual growth rates. When a lichen is wetted by rain or morning dew, it quickly absorbs the water and photosynthesis within its little algae partner is revived for a while. Since lichens are among the first plants to grow on bare rock, they play a role in soil formation by slowly etching the rock surface. Rock lichen can form a very strong attachment to the boulder it chooses for its home, making it impossible to scrape off. From the University of Wyoming Extension, I'm Mae Smith, exploring the nature of Wyoming.