Understanding of the structure and metabolism of connective tissue components in recent years has increased drastically.The support and attachment of the tooth in the bones of the jaw is provided by a complex comprising of four connectivetissues and is known as the Periodontium. It is attached to the dentine of the root by the cementum and to the bones ofthe jaw via the alveolar bone. Two of the connective tissues are mineralized and comprise of cementum and alveolarbone, while the other two are essentially fibrous in nature and are represented by the periodontal ligament (PDL) and thegingiva. This review article summarizes the current knowledge of the periodontium and will discuss the most importantvital structure in detail that is Periodontal ligament.