Shen Dan, the floorboard of Taoist medicine for preserving health and seeking immortality, is named after its red color, also known as "Da Dan", "Jin Dan" and "Huan Dan". Specifically, "Shen Dan" is mainly divided into exogenous Dan and endogenous Dan. As a noun of external elixir, it generally refers to the elixir synthesized by smelting and burning minerals, which can become immortal after taking it. For example, in the Classic of the Taishang Laojun, it is said: "Taoist priests refine mercury, sand-removing liquid, pearl jade and eight stones as elixirs, and offer a fesr to soar to the Heavenly Palace. It can also refer to one of the "nine kinds of pills", also known as the "magic spell". For example, "Bao Puzi's Inner Chapter Jin Dan" contains: "The second Dan is called Shen Dan, also known as the magic spell, which can become immortal after taking it for a hundred days. As a noun, Neidan generally refers to the process of refining gas, refining gas and refining spirit, and refining spirit to empty. Dan Cheng Can was also promoted to immortality. For example, in the second volume of A Record of Jin Ping Mei, different people presented Wang Zhongyang with five secret words about Inner alchemy, and told him, "For nine days at a time, I will turn my mind to alchemy, and my companion Penglai will go there." In addition, the cultivation of inner alchemy after Tang and Song Dynasties was mostly related to the "keeping the spirit" (keeping the mind) of the Wei, Jin and Qing Dynasties. In the art of guarding the gods, there was a saying that "the god of guarding the nine palaces". For example, the book "The cave is really too high, and the Taoist Yuan Dan gets the classics" says: "If you want to keep God, you should keep God. Males are nine inches long and nine minutes long. The surname is Lian, and the word is Arahiko. The female is six inches and six minutes long. Wearing the crown of the mysterious and golden fairy, he lived in Taihuali, Jiuguang Township, Shenfu above the Yuan Dynasty. These two people are the parents of Daxian Shengshen Dan. It is said that China's nickname "Aurora" in ancient India is actually the pronunciation of "Shen Dan".

Chinese Taoist Association and Suzhou Taoist Association: A Dictionary of Taoism (Beijing: Huaxia Publishing House, 1994).