What is "neidan"

Neidan, or internal alchemy , is an array of esoteric doctrines and physical, mental, and spiritual practices that Taoist initiates use to prolong life and create an immortal spiritual body that would survive after death. Also known as Jindan ("golden elixir"), inner alchemy combines theories derived from external alchemy (waidan), correlative cosmology (including the Five Phases), the emblems of the Yijing, and medical theory, with techniques of Daoist meditation, daoyin gymnastics, and sexual hygiene.

In Neidan the human body becomes a cauldron (or "ding") in which the Three Treasures of Jing ("Essence"), Qi ("Breath") and Shen ("Spirit") are cultivated for the purpose of improving physical, emotional and mental health, and ultimately returning to the primordial unity of the Tao, i.e., becoming an Immortal. It is believed the Xiuzhen Tu is such a cultivation map. In China, it is an important form of practice for most schools of Taoism.