  In these proceedings, we present the measurements of neutron skin thickness
and nuclear deformation using isobar $^{96}_{44}$Ru+$^{96}_{44}$Ru and
$^{96}_{40}$Zr+$^{96}_{40}$Zr collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV by
the STAR detector. The significant deviations from unity of the isobar ratios
of elliptic flow $v_{2}$, triangular flow $v_{3}$, mean $p_{\rm T}$
fluctuations $\langle\delta p_{\rm T}^{2}\rangle/\langle p_{\rm T}\rangle^{2}$,
and asymmetric cumulant ${\rm ac}_{2}\{3\}$ indicate large differences in their
quadrupole and octuple deformations. The significant deviations of the isobar
ratios of produced hadron multiplicity $N_{\rm ch}$, mean transverse momentum
$\langle p_{\rm T}\rangle$, and net charge number $\Delta Q$ indicate a
halo-type neutron skin for the Zr nucleus, much thicker than for the Ru
nucleus, consistent with nuclear structure calculations. We discuss how we
extract the neutron skin thickness, the symmetry energy slope parameter, and
deformation parameters from data.
