The direct imaging of reversible phase transitions observed in nanometer-sized bismuth (Bi) particles induced by surface charging under controlled electron-beam intensities, was analyzed. The nanoparticles were observed at a high magnification that is suitable for imaging of lattice fringes which were revealed using a very low electron current density. The electron irradiation in the electron microscope produced Bi grains of 5-10 nm at the surface of the Bi agglomerates and carbon films. The results show that Bi particles migrate towards the surface of the oxide or to the supporting carbon film.