  Emerging from the symbiotic combination of nanotechnology and communications,
the field of nanonetworking has come a long way since its inception more than
fifteen years ago. Significant progress has been achieved in several key
communication technologies as enablers of the paradigm, as well as in the
multiple application areas that it opens. In this paper, the focus is placed on
the electromagnetic nanonetworking paradigm, providing an overview of the
advances made in wireless nanocommunication technology from microwave through
terahertz to optical bands. The characteristics and potential of the compared
technologies are then confronted with the requirements and challenges of the
broad set of nanonetworking applications in the Internet of NanoThings (IoNT)
and on-chip networks paradigms, including quantum computing applications for
the first time. Finally, a selection of cross-cutting issues and possible
directions for future work are given, aiming to guide researchers and
practitioners towards the next generation of electromagnetic nanonetworks.
