Top panel: Kippenhahn diagram for the 1.5 M_⊙ star computed with thermohaline instability and rotation-induced mixing. Here we focus on the red giant branch. Green dashed lines delimit the hydrogen-burning shell above the degenerate helium core, and the dotted line shows the region of maximum nuclear energy production. The region where thermohaline instability takes place is indicated in blue. Bottom panel: evolution of ¹²C/¹³C during the RGB.