What is the so-called yin-yang science?

Yin-yang study means that what the eyes can see is Yin and what they can't see is Yang, that is, the invisible and the visible are adjusted to each other. This is Yin-yang study. It is antagonistic and inseparable. Everything has yin and yang, solitary yin is not born, and solitary yang is not long. Too broad, not just gossip and five elements. It is the study of heaven and earth.