Man, small universe, corresponding to heaven and earth. Therefore, Taoism believes that there are three treasures in the sky, namely the sun, the moon and the stars. There are three treasures on the earth, namely water, fire and wind. There are also three treasures in this small universe, essence, qi and spirit. Spirit is called three treasures, also known as three industries and three wonders. It is an important material basis of human life activities. "Exquisite and exquisite, vigorous and vigorous" leads to longevity; "Exhaustion of essence, exhaustion of qi and distraction" leads to death. Therefore, people's health and longevity depend entirely on the spirit, and the three are indispensable. In Taoist inner alchemy, vitality is a good medicine for inner alchemy. In the Taoist health preserving system, all spirits are the core content of cultivation. Taoism believes that in nature, there are three kinds of animals that are good at self-cultivation. Among them, deer is good at nourishing essence, turtle is good at refining qi, and crane is good at concentrating. Therefore, people who were good at keeping in good health in ancient times advocated imitating deer to nourish essence, and the Falun returned to inhale. (For example, the famous turtle breathing method is the health preserving method of Falun turtle breathing. (French crane absorbed. In ancient fairy tales, immortals often take cranes as companions, and the essence is that cranes are the representatives of gods. )