A brief historical survey of the conductive complexes formed between solvating molecules and metal salts is given here. The elucidation of the special conduction mechanism of these materials have been a challenging emulation for the scientific community. Yet, unsettled questions remain concerning the extend of dissociation and the transport numbers. These materials have up to now kept their promises for applications in batteries, and the technological implications of their use are now generally accepted and also apply to the newly considered gel electrolytes which are polymer-immobilized non-protic liquids.