... I work at the Osservatorio Astrofisico di Arcetri in the Star Formation Group . 8 M sun 4R sun 10 3 L sun , i.e. earlier than B3) than low-mass ZAMS stars. ... For this reason, understanding the mechanisms that give rise to the formation and evolution of massive stars is a fundamental tool to investigate the structure and evolution of the Galaxy. In spite of this, the early evolutionary stages of a high-mass star are still poorly understood, and many questions remain unresolved at the moment. ...