Rock growth is the process of rocks forming and changing over time. MOSS and LICHEN are two types of rock growth that can be seen in nature. MOSS is a small, soft plant that grows in clumps or mats in damp or shady locations. LICHEN is a composite organism made up of a fungus and an alga living together in a symbiotic relationship. Both MOSS and LICHEN are important components of the natural environment, providing food and shelter for many species of animals and plants.