Melting and solidification of indium nanocrystals grown on (002) highly oriented graphite is studied by reflection high-energy electron diffraction operating in a transmission mode through the outer shell of the nanocrystals. When recrystallized from the melt, evaporated indium grows as an ensemble of nanocrystals with particle size distribution that depends on the mean film thickness. Films with mean thickness from 0.5 to 34 ML are investigated. The intensity change of the diffraction pattern with temperature is used to probe the melting and solidification of the nanocrystals. The melting of indium nanocrystals starts at temperatures below the bulk melting temperature, depending on the size distribution of the nanocrystals. Melting continues over a temperature range extending up to that of bulk melting. The liquid skin model of melting and the homogenous melting model are shown to agree with the melting point size dependence. However, line profile analysis of the diffraction pattern shows a reduction in the crystalline volume within the probed shell at high temperatures. This indicates the formation of a liquid layer surrounding the nanocrystals and supports the liquid skin model. All films show supercooling by an amount that increases with the mean film thickness up to 6 ML and remains constant for films with larger mean thickness. (C) 2003 Elsevier B.V. All rights reserved.