  The jet quenching phenomenon in heavy ion collisions provides a strong
evidence of the modification of parton shower in the quark-gluon plasma. This
contribution focuses on the hard probes of QGP using jets and summarizes the
new theoretical progress of jet substructure modification studies using
effective field theory techniques. We emphasize the important role of jet
substructure observables as they probe various aspects of the jet formation
mechanism and allow us to study the medium properties in great details. The
precise calculations require the systematic resummation and consistently
including medium modifications. Specifically, we discuss the calculations of
jet shapes and cross sections in proton-proton and lead-lead collisions at the
LHC using soft-collinear effective theory, with Glauber gluon interactions in
the medium. In the end we present the comparison between our calculations and
the recent measurements at the LHC with very good agreement. We conclude that
precise jet modification studies in heavy ion collisions has been initiated.
