The university Qi energy creates Yin Yang.
Take a human as an example: a man is Yang, a woman is Yin; on a person, the front is Yang, the back is Yin; the upper is Yang, the lower is Yin; very importantly, the spirit is Yang, the body is Yin.
In the human body, the Yang meridian is active, warm, and fast; the Yin meridian tends to be still, cold, and slow. So, the meridian that runs on the inner side is called the Yin channel, and that on the outer side is called the Yang channel. With this principle in mind, let us raise the arm: the inner side of the arm is Yin with extraneous fat accumulated, the outer side is Yang of mostly muscles.
The function that runs the human body is Yang, and food/drink is Yin. The food/drink can provide the essential energy that maintains the function (Yang) of the body through biochemical actions and nourish the body (Yin) through gasification.
Yin Yang in the human body is relatively balanced. This means: human spirit and body are balanced; human functions and basic food/water energies are balanced.