Everything in the universe is energy, which can be classified as either Yin energy or Yang energy. The concept of Yin and Yang lies at the heart of many branches of classical Chinese science and philosophy. Yin and Yang affect everything in the universe, including ourselves. The Yin/Yang concept describes how contrary forces are interconnected and interdependent in the universe. Harmony can be achieved only if the Yin and Yang are balanced.
Yin is the moon and means darkness, coolness, moistness, and peacefulness. Yang is the sun and means brightness, dryness, warmth, and liveliness. Yang is the sky, and Yin is the earth; Yang is male, Yin is female. Yang grows everything, Yin shapes everything.
Yin and Yang are opposite each other, yet everything has both Yin and Yang aspects. The amount of each varies according to the specific object. They cannot exist without each other.
In the book of changes I Ching, Yin and Yang are represented by broken and solid lines: ☰ is heavily Yang, while ☷ is heavily Yin. Any other combinations of broken and solid lines such as ☴ or ☵ fall in between.
The balance of Yin and Yang is the basic principle of traditional Chinese medicine. Our body, mind, and emotions are all subject to the influences of Yin and Yang. When they are in balance, we feel good and healthy. If the balance is broken and one dominates the other, the imbalance will result in illness. Therefore, the treatment of the disease is the process of normalizing the proportion of Yin and Yang in the body. Once balance is achieved, the sickness is healed. | 
