Internal profiles from the 15 M_⊙ model taken near the end of the MS before expansion (left) and at the onset of core-He burning after expansion (right). The profiles show the stratification of density (top panel), local Γ_rad, gas-to-total pressure ratio β, and convection flux fraction (bottom panel). The blue shaded region indicates convective regions. The post-expansion model exhibits about nine orders of magnitude density contrast between the He-rich core and the envelope.