Quantum physics offers new possibilities to transmit information, and has led to both, secure and efficient ways of communication. Current efforts aim at extending the range of communication either using satellites or quantum repeaters, as well as at building networks for multi-partite communication. All this requires building distant quantum systems that can act as memories, process the information, and communicate with each other. Two of the most promising systems consist of atoms in high-quality cavities or NV-centers, connected by optical fibers. First protocols transferring information and entangling two nodes have already been demonstrated, and several basic principles of quantum repeaters have also been experimentally proved. However, the construction of large scale quantum networks allowing us to extend quantum communication beyond several hundreds of kilometers and, in general, quantum networks with several nodes, remain as an outstanding challenge. Furthermore, the development of protocols for those networks, as well as applications is a very active area of research. Researchers at both MPG and Harvard are among the leaders in this field. They pioneered and contributed to some of the main achievements in quantum communication, and are at the forefront of research in this area.