What is the theory of Yin and Yang?

Yin and Yang concept originated from the xia dynasty, based on a book in the xia dynasty book lianshan (" mountains ", "the facts", the zhouyi is three easy).The mountains have appeared in the book Yin hexagram and Yang hexagram.Yin-yang theory to the universe of all things is divided into two major categories of Yin and Yang, think that the formation and development of all things and movement, all is in the movement and transformation of Yin and Yang two gas.Concept of Yin and Yang, early from the alternation of night and day and sunshine among objects sunny side called Yang, shady side called Yin.Extended continuously, further extensive explain all the phenomena in the nature and society.After the concept of Yin and Yang as the theory of yin-yang is the zhou dynasty, especially theThe I ching"Sweeping generalization of Yin and Yang, the system, the complete theory of Yin and Yang.All bright, outside, top, thermal and dynamic, fast, male, the strong, the singular positive;All the inside of the dark, and the following, cold, quiet, slow, female, vulnerability, dual are negative.Both are interdependent, the unity of opposites.The ancients of dependence, opposites, transformation, with the modern world view of materialist dialectics and epistemology.