A new type of aromatic system, that of the-membered aromatic heterocycles, stabilized by p-p-p or p-p-d conjugation is discussed. The problem of carbenoid or inorganic compounds with electron valent shells similar to that of carbenes has been considered and it has been supposed that their reactions with multiple bonds can be used to obtain three-membered heterocycles. These conclusions are substantiated by the investigation of the reactions of bivalent silicon and germanium derivatives with diphenyl acetylene and acetylene. First representatives of the new type of heterocyclic, three-membered silicon and germanium heterocyclic compounds, have been prepared.