Tetrahedrane is a simple 'proposed' hydrocarbon in the family of 'platonic hydrocarbons'

It has a very simple chemical formula C₄H₄ , and calculations show that it should be relatively stable. Methods for making the compound are as yet unknown (although derivative molecules, e.g tetra-tert-butyl-tetrahedrane, have been made). Its chemical properties therefore remain theoretical.

Technical information at Wikipedia