The first book devoted to a systematic consideration of electronic excitations and electronic energy transfer in organic crystalline multilayers and organics based nanostructures(quantum wells, quantum wires, quantum dots, microcavities). The ingenious combination of organic with inorganic materials in one and the same hybrid structure is shown to give qualitatively new opto-electronic phenomena, potentially important for applications in nonlinear optics, light emitting devices, photovoltaic cells, lasers and so on. The book will be useful not only for physicists but also for chemists and biologists.To help the nonspecialist reader, three Chapters which contain a tutorial and updated introduction to the physics of electronic excitations in organic and inorganic solids have been included. * hybrid Frenkel-Wannier-Mott excitons * microcavities with crystalline and disordered organics * electronic excitation at donor-acceptor interfaces * cold photoconductivity at donor-acceptor interface * cummulative photovoltage * Feorster transfer energy in microcavity * New concepts for LEDs.