The aim of this proposal is to find a model to understand how molecules of diacylglycerol (DAG) insert in model membranes of natural composition (here the chloroplast envelope, containing mono- and digalactosyldiacylglycerol), addressing the possibility that they could invert their polar head orientation in this bilayer, possibly lying in a flat orientation in the core of the bilayer, as recently shown for cholesterol. It is essential to confirm this latter hypothesis in the case of DAG. Neutron reflectometry is a technique that has proved valuable in determining the structure and composition of these natural model membrane systems at the solid/liquid interface. This work is relevant in the study of lipid metabolism.