Well established as the fundamental theory of strong interactions, QCD has been predicted to undergo phase transition at high temperatures and/or densities. A novel state of matter, known as Quark-Gluon Plasma (QGP) resulting from the phase transition is currently intensively explored in relativistic heavy ion collision experiments at BNL-RHIC and CERN-LHC. This talk will be divided into two parts. In the first part, I will discuss theoretical aspects of QCD thermodynamics, in connection with my doctoral thesis work on non-perturbative studies of the chiral phase transition within the Dyson-Schwinger Equation approach. The second part will be devoted to QGP phenomenology, with focus on my recent work on open heavy flavor probes of the QGP, which represents developments of a formalism that consistently combines non-perturbative microscopic interactions for heavy quark diffusion with resonance recombination for heavy quark hadronization.