Neidan
Neidan, or internal alchemy (traditional Chinese: 內丹術; simplified Chinese: 內丹术; pinyin: nèidān shù), is an array of esoteric doctrines and physical, mental, and spiritual practices that Taoist initiates use in hopes to prolong life and create an immortal spiritual body that would survive after death. Also known as Jindan (金丹 "golden elixir"), internal alchemy combines theories derived from external alchemy (waidan 外丹), correlative cosmology (including the Five Phases), the emblems of the Yijing, and medical theory, with techniques of Taoist meditation, daoyin gymnastics, and sexual hygiene.