  The chiral crossover of QCD at finite temperature and vanishing baryon
density turns into a second order phase transition if lighter than physical
quark masses are considered. If this transition occurs sufficiently close to
the physical point, its universal critical behaviour would largely control the
physics of the QCD phase transition. We quantify the size of this region in QCD
using functional approaches, both Dyson-Schwinger equations and the functional
renormalisation group. The latter allows us to study both critical and
non-critical effects on an equal footing, facilitating a precise determination
of the scaling regime. We find that the physical point is far away from the
critical region. Importantly, we show that the physics of the chiral crossover
is dominated by soft modes even far beyond the critical region. While scaling
functions determine all thermodynamic properties of the system in the critical
region, the order parameter potential is the relevant quantity away from it. We
compute this potential in QCD using the functional renormalisation group and
Dyson-Schwinger equations and provide a simple parametrisation for
phenomenological applications.
