  Recent measurements of jet structure modifications at RHIC and LHC highlight
the importance of differential measurements to study the nature of jet
quenching. Since these jet structure observables are intimately dependent on
parton evolution in both the angular and energy scales, measurements are needed
to disentangle these two scales in order to probe the medium at different
length scales to study its characteristic properties such as the coherence
length. To that effect, the STAR collaboration presents fully unfolded results
of jet sub-structure observables designed to extract fundamental quantities
related to the parton shower via the SoftDrop shared momentum fraction, the
groomed jet radius, and the jet Mass in p+p collisions at 200 GeV as a function
of jet transverse momenta. We also showcase the first measurement of iterative
softdrop groomed observables for first, second and third splits with an
initiator prong transverse momenta ranging from 20-25 GeV. In comparing the
un-corrected data to our simulation, we are able to look at snapshots of the
jet clustering history leading towards an understand of the time evolution of
the parton shower. Having established the p+p baseline, we present the first
measurement of the jet's inherent angular structure in Au+Au collisions at 200
GeV via an experimentally robust observable the opening angle between the two
leading sub-jets ($\theta_{SJ}$). In Au+Au collisions at STAR, we utilize a
specific di-jet selection as introduced in our previous momentum imbalance
($A_{J}$) measurement and measure both the $A_{J}$ and the recoil jet spectra
differentially as a function of the angular classes based on the $\theta_{SJ}$
observable. With such measurements, we probe the medium response to jets at a
particular resolution scale and find no significant differences in quenching
for jets of different angular scales as given by $\theta_{SJ}$.
