  We present the first 3-dimensional simulations following the evolution of
supernova shocks from their inception in the stellar core through the
development of a supernova remnant into the Sedov phase. Our set of simulations
use two different progenitors and two different conditions for the structure of
the circumstellar environment. These calculations demonstrate the role that
supernova instabilities (the instabilities that develop as the shock drive
through the star) play in defining the structure and long-term development of
instabilities in supernova remnants. We also present a first investigation of
the mixing between stellar and interstellar matter as the supernova evolves
into a young supernova remnant.
