Who did Raphael model his portrait of Heraclitus?

Raphael modeled his portrait of Heraclitus after the Italian philosopher Michelangelo. In the famous fresco "The School of Athens," Heraclitus is depicted with a brooding expression, reflecting Michelangelo's own demeanor and philosophical depth. This choice highlights the connection between the two artists and underscores the theme of intellectual struggle present in the artwork.