Contents 1 Introduction. 2 The main experimental findings. 3 The microscopic description of the quarkgluon medium. 3.1 Color Glass Condensate, Glasma, Quark-Gluon Plasma. 3.2 Jet quenching and parton energy loss in dense non-abelian medium.4 The macroscopic approach to the quarkgluon medium. 4.1 Equations of the in-medium QCD. 4.2 The chromopermittivity. 4.3 Classical polarization effects in the quark-gluon medium and its chromodynamical properties. 4.4 Instabilities at high energies. 4.5 Nonlinear effects and the color rainbow. 4.6 Hydrodynamics (thermodynamical and mechanical properties of Quark-Gluon Plasma.