Dendrimers are a unique class of nano-structured vehicles for drug and gene delivery into intracellular targets. Their surface chemistry influences their transport across epithelial and endothelial barriers. Dendrimer endocytocis via caveola/lipid rafts is markedly dependant on the dendrimer surface chemistry. However, the mechanisms of interactions are so far unknown. Cationic dendrimers are believed to adsorb to negatively charge surface of cell membranes and form complexes with lipids called ¿dendrisomes¿, opening channels in the cell membrane. Negative dendrimers are uptaken trough caveola endocytosis, while cationic and neutral dendrimers are taken by caveola- and clathrin-independent pathways. Neutron reflectivity will allow identifying where are dendrimers colocalized within supported lipid membranes and therefore help elucidating the mechanisms behind dendrimer uptake by cells