Hard scattered partons are used to probe the hot and dense QCD matter that is created in heavy-ion collisions. As a parton passes through the QCD medium, induced energy loss from elastic and radiative interactions leads to a modification of the parton shower; this modification is used to deduce medium properties. Early measurements of the nuclear modification factor at RHIC have already provided evidence of parton energy loss in heavy-ion collisions, and in more recent years LHC experiments have confirmed these findings and greatly extended their kinematic range.

This talk will give a brief introduction to `hard probes' (covering high-pt single particles and jets) and shows how systematic comparison of models to experimental results can be used to extract transport parameters of the QGP. Jet suppression and the modification of the jet shape are used to further the understanding of the nature of parton energy loss. New developments - theoretical and experimental - in combining energy-loss measurements to the parton in-medium path-length will be discussed, covering di-jet measurements (including di-jet asymmetry with respect to the event plane) as well as jet $v_2$. These observables are compared to results from the JEWEL Monte Carlo, and raise the question of what the balance between per-jet energy loss fluctuations and average energy-loss from medium geometry is.