The crystal growth process in colloidal nanocrystal systems is usually associated with the Ostwald-ripening mechanism. Here, we report on experimental evidence indicating that another crystal growth process took place in a colloidal nanocrystal system at room temperature. This crystal growth process is based on grain rotation among neighboring grains, resulting in a coherent grain–grain interface, which, by eliminating common boundaries, causes neighboring grains to coalesce, thereby forming a single larger nanocrystal. This phenomenon was observed in ${\mathrm{SnO}}_2$ nanocrystals (particle size ranging from 10 to 30 Å).