Taiji (太極) is a state of being from Tao and Wuji. It is a state of absolute, and of infinite potentiality. In Tao Te Ching, Tao manifested as One, which is Taiji. In a Taoist guidance book, the same verse was amplified as out of Tao came Taiji, which then split into yin and yang or Two Aspects, yin and yang slitting into the Four Realms, Wu xing the Five Elements, and from there the world was created.
Taiji was a state in which the world became intelligible before creation. Taiji may be equated to the One, Oneness, Unity, as in attaining One or Unity (得一)  and as stated in the Tao Te Ching.