Together, this Chinese compound word means life, which is the central theme of Chinese alchemy - to promote longevity of life to immortality.

In the viewpoint of ancient Taoist of the Chinese alchemy school, Buddhism only cultivates xėng, the spiritual or mental aspect of life while Taoism cultivates also mėng, the physiological aspect of life, so called "cultivate both life and innate nature" .

There are also different Taoist schools of Chinese alchemy that places different emphasis on this. For example, the Quanzhen School or the North sect emphasize more on cultivating xėng, while the South sect emphasize more on cultivating mėng, so called the difference between "first innate nature then life" and "first life then innate nature" .