We will study the detailed mechanism responsible for the self-assembly of gold nanoparticles (Au NPs) at the air/liquid interface by specular neutron reflectometry and grazing incidence small angle neutron scattering (GISANS). Spherical and anisotropic gold nanoparticles will be included in the study to assess the influence of the shape and size on the kinetics of assembly as well as on the resulting arrangement on the nanoscale. It is well known that the interfacial assembly of colloidal particles yields the formation of largedomains of oriented crystalline structures. Besides, GISANS has been limited to solid/liquid and solid/air interfaces up to now. To the best of our knowledge, no liquid/air GISANS experiment probing a single layer has been reported. We will, therefore, perform a reference measurement on FIGARO with a well-known system composed of high loading of Au NPs on D2O to unambiguously show the possibility of air/water GISANS on FIGARO.