"Man's life is the result of the concentration of energy. If energy concentrates, life manifests, if energy disperses, death ensues." Zhuang Zi.
	Acupuncture, moxibustion, phytotherapy (medical herbs), nutrition, exercizing (Tai Chi, Qi Gong) are essential components of the Traditional Chinese Medicine (T.C.M.). It corresponds to a theoretical and phylosophical system sustained on research and observation over the last milennia, a dialectical way of thinking which studies the laws that rule the macrocosm as well as the microcosm. The Yin-Yang, the five element theory, the Zang-Fu, the essence, the Qi, the blood (Xue), the body fluids, the meridians, the etiology, the pathogenesis, the diagnostic methods and the rules of prevention and treatment are the pillars of a healthy and long life.
		Yang is the realm of luminous, the heaven, the well-lit, the expansible, all activity, all outward expression, that which rises, that which shines. Yin is the realm of the internal, the earth, the dark, that which descends, that which retreats, the reduction of activity, the repose.
	In the beginning the Universe was in "Wu-Chi" (which means "empty", "there is nothing"). Like an egg full of a "sea of air" it started to move changing continuosly. Out of that movement water was formed (by the five element theory). And water produced wood and wood produced fire.The fire heated up and expanded that "sea of air", that "egg", and a big explosion occurred (Big Bang?). From that explosion, the clearer and lighter particles rose towards the heaven: the Yang. Between the heaven and the earth are Man and Nature. Hereby we have the Yin-Yang principle defined within the triagram concept: Earth-Man-Heaven.
		"When the Qi of the earth rises clouds are formed; when the Qi of the heaven descends, it rains."
	As night and day, heat and cold, movement and stillness. "Movement and changes in Yin Yang fosters development and change in all things." This is explained in the Chapter "Manifestations of Yin and Yang" in the Suwen, the interdependence between opposites and complementaries.
		All Qi blocking or Qi stagnation leads to disturbances, which may express themselves physically, spiritually or in the psychic realm.
	The "concentration of energy" which gives form to all things, must flow harmoniously in the human body in accordance with the different seasons, hours or ages and must be free from obstacles (external and internal factors, emotions) in order for the person to feel healthy. The Qi is transformed into substance but its essence is invisible. What we see of it is only its expression (which is in the macrocosm, as well as in the microcosm, our body).