Pyrene is a polycyclic aromatic hydrocarbon (PAH) composed of four fused benzene rings. It is a colorless, crystalline solid that is insoluble in water but soluble in organic solvents. Pyrene is commonly found in coal tar and is produced during the incomplete combustion of organic materials. In addition to its presence in the environment, pyrene is used in scientific research and as a fluorescent probe in various applications. It can also be found in some commercial products, including dyes and plastics. Due to its potential health effects, pyrene is monitored in environmental studies.