Relativistic heavy-ion collisions allow the experimental study of QCD under extreme conditions. In particular, in the initial stages right after the collision, an out-of-equilibrium QCD plasma is created, which later isotropizes and allows for a hydrodynamic description. In this talk, I will discuss how to describe these initial far-from-equilibrium stages using QCD kinetic theory, and how the non-equilibrium plasma may influence the propagation of high-energy particles (jets) that can be measured in the experiment.