The so-called environmental health care refers to the external conditions that are formed by air, water, sunshine, soil, vegetation, housing, social humanities and other factors and are conducive to human life and work. In China's traditional philosophy, the relationship between man and nature is an organic whole. A suitable living environment can ensure normal work and residence, promote human health and longevity, and contribute to the prosperity of the nation. On the other hand, all kinds of harmful substances produced in human production and life activities will not only endanger human health, but also cause long-term potential harm and threaten future generations if they are not handled properly. Epidemiological studies have proved that 70%~90% of human diseases are related to the environment. If human beings want to live a long and healthy life, they must establish and maintain a harmonious relationship with the external environment.

Sleep is an important means to balance yin and yang of human body, the best energy conservation, the best reserve and charging, and the first prescription to recover fatigue and get out of sub-health.

The sleep mechanism of TCM is that you will fall asleep when Yin Qi is abundant, and you will wake up when Yang Qi is abundant. So you should go to bed before midnight (2 1-23 o'clock) and get into the best sleep state at midnight. Because according to the sleep theory in Huangdi Neijing, midnight is the meeting of Yin and Yang, and fire and water meet Thai, which is called "closing Yin". It is the heaviest time of the day when Yin dominates quietness, so I want to sleep at midnight.

All in all, these two are the ways of keeping in good health discovered by our ancestors.