  We discuss the emergence of a low-energy effective theory with quarks,
mesons, diquarks and baryons at vanishing and finite baryon density from first
principle QCD. The present work also includes an overview on diquarks at
vanishing and finite density, and elucidates the physics of transitional
changes from baryonic matter to quark matter including diquarks. This set-up is
discussed within the functional renormalisation group approach with dynamical
hadronisation. In this framework it is detailed how mesons, diquarks, and
baryons emerge dynamically from the renormalisation flow of the QCD effective
action. Moreover, the fundamental degrees of freedom of QCD, quarks and gluons,
decouple from the dynamics of QCD below the respective mass gaps. The resulting
global picture unifies the different low energy effective theories used for low
and high densities within QCD, and allows for a determination of the respective
low energy constants directly from QCD.
