Neidan, a Chinese method of internal Alchemy. Part of the Chinese Alchemical tradition that was separated into internal and external (Waidan) at some point in the beginning of the Tang Period.

The Neidan tradition of internal alchemy was practised by working with the energies that were already present in the human body, as opposed to using natural substances, medicines or elixirs, from outside of the body. It's said that the Shangqing (Supreme Clarity) tradition of Daoism played an important role in the emergence of Neidan alchemy, after using Wiedan mainly as a meditative practise, and therefore turning it from an external to an internal art.

Closely related to Daoism, it is believed that the goal of Neidan was to merge the two energies of Yin and Yang, and return to the primordial unity of the Tao.