To investigate the structure of the protein assemblies formed in situ, we carried out neutron reflectometry experiments (Figure ). We used a previously reported protocol in which a thin liquid film was formed at the surface of a silicon substrate (hydrophobised) and frozen prior to positioning at an aqueous (PBS) interface pre-cooled to preserve the thin film morphology, followed by warming up of the aqueous and oil phases and melting to form the liquid-liquid interface . Note that as the melting temperature of Novec 7500 was too low, it was not possible to carry out this procedure with this fluorinated oil, and hexadecane had to be used instead.