  The ALICE collaboration at the CERN LHC reports novel measurements of jet
substructure in pp collisions at $\sqrt{s}$= 7 TeV and central Pb-Pb collisions
at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Jet substructure of track-based jets is
explored via iterative declustering and grooming techniques. We present the
measurement of the momentum sharing of two-prong substructure exposed via
grooming, the $z_{\rm{g}}$, and its dependence on the opening angle, in both pp
and Pb-Pb collisions. We also present the first measurement of the distribution
of the number of branches obtained in the iterative declustering of the jet,
which is interpreted as the number of its hard splittings. In Pb-Pb collisions,
we observe a suppression of symmetric splittings at large opening angles and an
enhancement of splittings at small opening angles relative to pp collisions,
with no significant modification of the number of splittings. The results are
compared to predictions from various Monte Carlo event generators to test the
role of important concepts in the evolution of the jet in the medium such as
color coherence.
