  We present the first three dimensional (3D) simulation of the final minutes
of iron core growth in a massive star, up to and including the point of core
gravitational instability and collapse. We self-consistently capture the
development of strong convection driven by violent Si burning in the shell
surrounding the iron core. This convective burning builds the iron core to its
critical (Chandrasekhar) mass and collapse ensues, driven by electron capture
and photodisintegration. The non-spherical structure and motion (turbulent
fluctuations) generated by 3D convection is substantial at the point of
collapse. We examine the impact of such physically-realistic 3D initial
conditions on the core-collapse supernova mechanism using 3D simulations
including multispecies neutrino leakage. We conclude that non-spherical
progenitor structure should not be ignored, and has a significant and favorable
impact on the likelihood for neutrino-driven explosions.
