The production of Solanum nigrum depends on the filling of essence in the kidney, which is related to the growth and reproduction of human body. Tiangui is the key driving force for women's growth and development, and insufficient or excessive Tiangui will make women suffer from gynecological diseases.
Solanum nigrum is a subtle substance produced when the essence of human kidney is filled to a certain age, which was called "invisible water" by the ancients.