  This is a didactic review of spectral and dynamical properties of atoms and
molecules at energies below the ionization threshold, the focus being on recent
work in which the author was involved. As far as possible, the results are
described using a simple model with \emph{one} electron only, and with
\emph{scalar} bosons. The main ideas are explained but no complete proofs are
given. The full-fledged standard model of non-relativistic QED and various of
its aspects are described in the appendix.
