  The numerical simulation of turbulence in stars has led to a rich set of
possibilities regarding stellar pulsations, asteroseismology, thermonuclear
yields, and formation of neutron stars and black holes. The breaking of
symmetry by turbulent flow grows in amplitude as collapse is approached, which
insures that the conditions at the onset of collapse are not spherical. This
lack of spherical symmetry has important implications for the mechanism of
explosion and ejected nucleosynthesis products. Numerical resolution of several
different types of three--dimensional (3D) stellar simulations are compared; it
is suggested that core collapse simulations may be under-resolved.
  New physical effects which appear in 3D are summarized.
  Connections between simulations of progenitor explosion and observations of
supernova remnants (SNR) are discussed.
  Present treatment of boundaries, for mixing regions during He--burning,
requires revision.
