In-situ x-ray diffraction allowed us to track the melting process of nanosized Sn droplets obtained by Sn evaporation on a substrate heated above the Sn melting temperature. We provide further evidence that the melting temperature of nanosized Sn particles is dramatically decreased with respect to the bulk value. The results, obtained by the analysis of in-situ x-ray diffraction patterns, indicate that thermal expansion of lattice parameters is anisotropic, the differences being related to the tetragonal crystal structure of beta-Sn. Moreover, the behavior of Sn-Sn distance against the temperature suggests that the melting temperature is related to a critical Sn-Sn distance. (C) 2003 American Institute of Physics.