  We summarize recent results for the spectrum and properties of light
pseudoscalar and scalar hadrons in a functional approach to QCD using
Dyson-Schwinger and Bethe-Salpeter equations. We focus in particular on the
role of pions as virtual constituents in light mesons ('pion cloud effects') as
well as their role as constituents of tetraquark bound states. An extension of
our framework into the charm quark sector reveals an all-charm tetraquark in
the mass region around 5.5 GeV.
