emblematic serpent of ancient Egypt and Greece represented with its tail in its mouth continually devouring itself and being reborn from itself. A Gnostic and alchemical symbol, Ouroboros expresses the unity of all things, material and spiritual, which never disappear but perpetually change form in an eternal cycle of destruction and re-creation.

In the 19th century, a vision of Ouroboros gave the German chemist Friedrich August Kekule von Stradonitz (Kekule von Stradonitz, August) the idea of linked carbon atoms forming the benzene ring.