Notes on the Fetal Breath Sutra, originally titled "Mr. Huan Zhen's Notes". Mr. Huan Zhen is suspected to be a Taoist priest from the Tang Dynasty. Volume 60 of "Yunji Qizhu" has been included in this article. This book is also included in the Jade Jue category of the Dongzhen Department of the Zhengtong Taoist Canon. It is in the same volume as the Three Sutras "Fetal Breathing Secret Essential Song Jue" and "Taiqing Zhenren Luo Ming Jue". "Fetal Breathing Sutra Commentary" is followed by "Fetal Breathing Inscription". In addition, this sutra is also included in "Tao Zang Ji Yao" and "Tao Zang Essence Record". The whole article is only a few hundred words long, and briefly outlines the key points of the inner alchemy family's cultivation of Shen Qi. Note: "Taoist cultivators often place their Qi under their navel to keep their spirit within their body. The combination of the divine Qi creates a mysterious fetus. Once the Xuan Fei is formed, it generates its own body, which is the inner elixir of immortality." This means that the "fetus" is formed from under the navel (also known as the "lower Dantian" or "Xuanfei"). "Fetal breath" means to keep the Qi below the navel in the human body. By keeping the "Qi", you can keep the "Shen", because the gods and the Qi are inseparable from each other. Only by keeping the soul inseparable can immortality be realized. In addition, if people want to keep God, they must also cling to emptiness to nourish their spiritual energy, that is, eliminate all emotions and thoughts, and do not let God come and go. Over time, God will be able to live forever and never leave the human body.