  Dyson-Schwinger equations furnish a Poincare' covariant framework within
which to study hadrons. A particular feature is the existence of a
nonperturbative, symmetry preserving truncation that enables the proof of exact
results. Key to the DSE's efficacious application is their expression of the
materially important momentum-dependent dressing of parton propagators at
infrared length-scales, which is responsible for the magnitude of
constituent-quark masses and the length-scale characterising confinement in
bound states. A unified quantitative description of light- and heavy-quark
systems is achieved by capitalising on these features.
