I plan to start this presentation with an overview of our work over the past decade on the efficient coupling of light and single quantum emitters, leading to the single-photon communication of two individual molecules at long distances . In this context, we will also discuss new results on a high-efficiency triggered source of single photons  and coherent nonlinear optical phenomena, which let a single organic molecule act as an efficient switch for weak beams of light . The long-term goal of these projects is to establish a platform for nano-quantum-optical operations and cooperative interactions in a mesoscopic system of photons and quantum emitters [4, 5]. In order to achieve this, we have developed novel microcavity  and chip-based nanoguide circuitry  for use at cryogenic conditions.References: Y. Rezus, et al., Phys. Rev. Lett. 108, 093601 (2012).  X-L. Chu, et al., Nature Photonics, 11, 58 (2017). A. Maser, et al., Nature Photonics 10, 450 (2016). S. Faez, et al., Phys. Rev. Lett. 113, 213601 (2014).  H. Haakh, et al., Phys. Rev. A, 94, 053840 (2016). D. Wang, et al., Phys. Rev. X, under review. P. Türschmann, et al., submitted.