Colloidal nanoparticles are widely used due to their specific electronic, chemical and biological properties. E.g. colloidal gold (Au) may form two- and three-dimensional structures comprising monolayers of hexagonally-packed Au nanoparticles. Such materials are promising systems for, e.g. nano-sized strain gauges. The applicability of such thin-film materials may of course be limited by the mechanical or thermal stability. Hence, an in-situ method like temperature-controlled grazing-incidence small-angle X-ray scattering (GISAXS) is an ideal tool for studying the thermal properties of such self-assembled thin-film structures.