We have developed a new thin-film differential scanning calorimetry technique that has extremely high sensitivity of 0.2 nJ. By combining two calorimeters in a differential measurement configuration, we have measured the heat capacity and melting process of Sn nanostructures formed via thermal evaporation with deposition thickness down to 1 Å. The equivalent resolution of the calorimeter is 1 nanogram in mass or 0.4 Å in thickness. We have observed a decrease of up to 120°C in the melting point of Sn nanostructures. ©1997 American Institute of Physics.