Both the Heavenly Stems and Earthly Branches belong to the Five Elements, but each has its own system and there is no mutual restraint. However, the Five Elements combined with Heavenly Stems and Earthly Branches will influence each other. In order to facilitate understanding, the concept of Nayin Five Elements is introduced. For example, Heavenly Stem Jia (the five elements are wood), Earthly Branch Shen (the five elements are metal), metal originally restrains wood, but Jia Shen Na Yin and the five elements are spring water.