What is the relationship between Qi and Yin and Yang?

Everything that is Yin(阴) contains some element of Yang(阳), and everything that is Yang contains some element of Yin. There is nothing so solid or material (Yin) that does not contain some energetic vibration (Yang), and nothing so kinetic or immaterial (Yang) that does not also contain some material substance (Yin). Even light, so Einstein tells us, has mass.

Yin and Yang are continuously changing; they constantly adjust to one another, and are endlessly transforming one into the other in an eternal dance of becoming. This wonderful concept of change is beautifully illustrated in the simple image of the "Yin-Yang symbol."

When all of the Yin and Yang aspects of Qi are in harmony with one another, there is health, wellbeing and contentment. When Yin and Yang are in disharmony, when there is too much or too little of one aspect of Qi relative to another, then there is illness, pain and suffering.

How are the concepts of Qi and Yin and Yang applied in TCM?

TCM provides guidelines for both the practitioner and patient on how to best facilitate harmony between Yin and Yang in any set of circumstances and how to create and circulate an abundance of Qi to sustain health and wellbeing. These are the "stems" of TCM that spring from the root concepts of Qi and Yin and Yang.