The formula of benzene (C6H6), caused a mystery for some time after its discovery, as no proposed structure could take account of all the bonds (carbon usually forms four single bonds and hydrogen one).

The chemist Kekulé was the first to deduce the ring structure of benzene; after years of studying carbon bonding, benzene and related molecules, the solution to the benzene structure came to him in a dream of a snake eating its own tail. Upon waking was inspired to deduce the ring structure of benzene.

While his claims were well publicized and accepted, by the early 1920s Kekulé's biographer came to the conclusion that Kekulé's understanding of the tetravalent nature carbon bonding depended on the previous research of Archibald Scott Couper (1831-1892); further, the German Chemist Josef Loschmidt (1821-1895) had earlier posited a cyclic structure for benzene as early as 1862, although he had not actually proved this structure to be correct.