We have developed a new class of solution processible organic-inorganic hybrids based on monodispersed semiconductor nanocrystals and conjugated oligomers (polymers). These new nanomaterials can act as active components in organic and molecular electronics. The organic-inorganic nanohybrids can be obtained in a three step procedure involving nanocrystals synthesis (CdSe, ZnSe etc), exchange of the initial surface ligands by bi-functional ones, and finally attaching the conjugated oligomers (polymers) on the functionalized nanocrystal surface either by grafting or by molecular recognition procedures. Two families of the polyconjugated molecules have been investigated: oligo- and polyanilines and oligo- and polythiophenes. As the obtained nanohybrids can be considered as an association of two electrochemically active systems of different nature, we have studied their voltammetric and spectroelectrochemical (UV-visible-NIR, Raman, EPR) behaviour. In several cases, the resulting properties have shown synergic rather than additive nature, proving that the obtained nanohybrids are not simple adducts but constitute a new class of organic-inorganic nanomaterials in which both components strongly interact. The conjugated surface ligands in the prepared nanohybrids can be reversibly switched between their semi-conducting and their conducting states, either electrochemically, by imposing an appropriate potential, or chemically, by selecting an appropriate doping reaction. Thus, the obtained systems can be considered as semiconductor-semiconductor or semiconductor-conductor molecular junctions of a new type.