  We are discussing the properties of the QCD vacuum which might be important
especially for the understanding of hadrons with small quark core size
$\sim0.3\,fm.$ We assume that at these distances the QCD vacuum can be
described by the Instanton Liquid Model (ILM). At larger distances, where
confinement is important, ILM should be extended to Dyons Liquid Model (DLM).
The ILM has only two free parameters, average instanton size
$\rho\approx0.3\,fm$ and average inter-instanton distance $R\approx1\,fm$, and
can successfully describe the key features of light hadron physics. One of the
important conceptual results was prediction of the momentum dependent dynamical
quark mass $M\sim(packing\,\,fraction)^{1/2}\,\,\rho^{-1}\approx360\,MeV$,
later confirmed numerically by evaluations in the lattice. The estimates show
that gluon-instanton interaction strength is also big and is controlled by the
value of dynamical gluon mass $M_{g}\approx M$. Heavy quarks interact with
instantons much weaker. The heavy quark-instanton interaction strength is given
by $\Delta m_{Q}\sim packing\,\,fraction\,\,\rho^{-1}\approx70\,MeV.$
Nevertheless, the direct instanton contribution to the colorless heavy-heavy
quarks potential is sizable and must be taken into account. At small distances,
where one-gluon exchange contribution to this potential is dominated, we have
to take into account dynamical gluon mass $M_{g}$. Also, instantons are
generating light-heavy quarks interactions and allow to describe the
nonperturbative effects in heavy-light quarks systems.
