  The jet shape is a classic jet substructure observable that probes the
average transverse energy profile inside a reconstructed jet. The studies of
jet shapes in proton-proton collisions have served as precision tests of
perturbative Quantum Chromodynamics (QCD). They have also recently become the
baseline for studying the in-medium modification of parton showers in
ultra-relativistic nucleus-nucleus collisions. The jet shape is a function of
two angular parameters $R$ and $r$, which can be at hierarchical scales. Its
calculation suffers from large logarithms of the ratio between the two scales,
and these phase space logarithms can conveniently be resummed in the framework
of soft-collinear effective theory (SCET). We find that, up to power
corrections, the integral jet shape can be expressed in a factorized form which
involves only the ratio between two jet energy functions. Resummation is
performed at next-to-leading logarithmic order using renormalization-group
evolution techniques. Comparisons to jet shape measurements at the LHC are
presented to verify the dominant role of the collinear parton shower and to
identify the kinematic region in which power-suppressed soft modes and
non-perturbative effects may play a role.
