Engineered nanoparticles (NPs) found large application in medicine as theranostic materials for the diagnosis and therapy of many diseases. The understanding of the interactions of NPs with cell membranes is of fundamental importance both to tune the efficiency of NPs entry in the cell and limit their cytotoxicity. Neutron reflectometry (NR) is a powerful technique widely used to examine supported lipid bilayers (SLB) morphology and their response to different effectors. We propose the use of this tool to understand the nature of the interaction between NPs and supported lipid bilayers (SLBs), used as model of the cell membrane, in vitro and in a relevant biological environment when NPs are in contact with proteins and form a new biological entity called protein corona NPs (PC).