Sporopollenin is a biological polymer found as a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically very stable (one of the most inert among biopolymers)  and is usually well preserved in soils and sediments. The exine layer is often intricately sculptured in species-specific patterns, allowing material recovered from (for example) lake sediments to provide useful information to palynologists about plant and fungal populations in the past. Sporopollenin has found uses in the field of paleoclimatology as well. Sporopollenin is also found in the cell walls of several taxa of green alga, including Phycopeltis (an ulvophycean) and Chlorella.
Spores are dispersed by many different environmental factors, such as wind, water or animals. In suitable conditions, the sporopollenin-rich walls of pollen grains and spores can persist in the fossil record for hundreds of millions of years, since sporopollenin is resistant to chemical degradation by organic and inorganic chemicals.