Man Follows Earth, Earth Follows Heaven, Heaven Follows Tao, Tao Follows Its Own Nature
This chapter gives the Tao Te Ching's closest thing to a creation account, naming the nameless source of everything and tracing a chain of dependence that ends, remarkably, in the Tao depending on nothing but itself.
Chapter 25 describes something "formed in chaos, born before heaven and earth" — silent, empty, standing alone and unchanging, moving in a great circuit without exhaustion — which Laozi says he does not know how to name, so he calls it Tao (道), and forces the word "great" (大) onto it for lack of better language. The chapter then lays out a hierarchy of following (法, fǎ, literally "to model oneself on"): humanity models itself on earth, earth on heaven, heaven on the Tao. The final link breaks the chain rather than extending it — Tao models itself on ziran (自然), its "own-so-ness" or spontaneous nature, meaning there is no further external standard the Tao answers to. This is the philosophical bedrock under everything else in the text: authority and order run all the way down to something self-caused, and human conduct is asked to align itself, indirectly, with that same self-sufficiency.
Heaven follows the Tao; the Tao follows what is natural.
"Ziran," rendered here as "its own nature," literally means "self-so" and became one of the most important terms in later Daoist philosophy, denoting spontaneous, uncaused being.
Tao Te Ching