  We present an overview of the framework of macroscopic quantum
electrodynamics from a quantum nanophotonics perspective. Particularly, we
focus our attention on three aspects of the theory which are crucial for the
description of quantum optical phenomena in nanophotonic structures. First, we
review the light-matter interaction Hamiltonian itself, with special emphasis
on its gauge independence and the minimal and multipolar coupling schemes.
Second, we discuss the treatment of the external pumping of quantum-optical
systems by classical electromagnetic fields. Third, we introduce an exact,
complete and minimal basis for the field quantization in multi-emitter
configurations, which is based on the so-called emitter-centered modes.
Finally, we illustrate this quantization approach in a particular hybrid
metallodielectric geometry: two quantum emitters placed in the vicinity of a
dimer of Ag nanospheres embedded in a SiN microdisk.
