Meibomian lipids spread on the surface of tears to enable formation of a stable film. Our data show that meibum forms duplex films that have physical properties not emulated by its major components: cholesterol and wax esters (CE, WE); and the surfactant (omega-acyl)-hydroxy-fatty acids (OAHFAs). Our X-ray reflectivity experiments show it has a 3-phase structure at low concentrations and Bragg peaks occur at high surface pressures indicating repeating layers. Our initial neutron reflectivity studies, interrupted by beam downtime, indicate that the OAHFAs and not wax esters lead to the repetitive layers. We now plan to use neutron reflectometry of meibomian lipid films seeded with deuterated-WEs, -CEs and -OAHFAs held at high pressures to determine the structure of the TFLL. The appearance of Bragg peaks for OAHFA seeded films will indicate they are responsible for multilayers.