Essence is the material base of Qi, even a form of special liquid Qi. Qi is derived from Essence and functional Qi produces Essence. Essence is closely related to Primordial Qi. Essence seems to be liquefied Qi, and Qi the vapor of Essence; both are changeable substances of matter, energy, and information. Abundant Congenital Essence makes Primordial Qi vigorous, and vigorous Qi induces more acquired Essence.