Yuanqi refers to qi in its original state, with yuan (元) denoting the beginning or the initial point. Yuanqi can neither be defined by shape nor be attributed to yin or yang. It existed prior to the emergence of heaven, earth, and all the things in between. After experiencing certain changes, it was separated into the qi of yin and yang, or that of heaven and earth. Hence the generation of all the things between heaven and earth. Some ancients regarded yuanqi as the origin of the world, while others believed that it was derived from the void, a more primitive state of being. Yuanqi sometimes refers to the qi that constitutes human bodies and all the other things in general.