  We review the major advances in understanding the morphologies and kinematics
of supernova remnants (SNRs). Simulations of SN explosions have improved
dramatically over the last few years, and SNRs can be used to test models
through comparison of predictions with SNRs' observed large-scale compositional
and morphological properties as well as the three-dimensional kinematics of
ejecta material. In particular, Cassiopeia A -- the youngest known
core-collapse SNR in the Milky Way -- offers an up-close view of the complexity
of these explosive events that cannot be resolved in distant, extragalactic
sources. We summarize the progress in tying SNRs to their progenitors'
explosions through imaging and spectroscopic observations, and we discuss
exciting future prospects for SNR studies, such as X-ray microcalorimeters
