Evolution of a M_ZAMS = 50 M_⊙ star at 0.1 Z_⊙ from M_α_ML1.82_MLTpp until ∼ 70% of its envelope mass becomes convective. Top panel: HR diagram. We show the HR position of the star when M_env, conv is 1, 5, 10, 20, 30, 40, 50, 60 and 70% of M_env. Bottom panel: Kippenhahn diagram, with radial evolution represented by the red line. In cyan, purple and gray respectively the convective, semiconvection and overshooting regions, while the green line represent the post-MS core-envelope boundary. The dashed vertical lines have the same colors of the scatter points in the left panel and represent the evolutionary stage at which the star reaches its respective M_env, conv/M_env ratio.