Cell adhesion and proliferation at the surface of liquids such as oil droplets is a surprising phenomenon as it is typically accepted in the field of bioengineering that cells require solid substrates to adhere and to exert mechanical forces. Our laboratory recently reported such observations and uncovered that such phenomenon was mediated by a nanoscale (15-20 nm) mechanically strong protein film (nanosheet) assembled at the liquid/liquid interface. We have also discovered that the molecular weight of surfactant (PLL) used strikingly influenced their mechanical behaviour: high molecular weight PLL form tougher nanosheets and sustain cell adhesion and expansion. This project aims to explore the structure of protein nanosheets assembled at analogous oil-water interfaces, in situ as a function of nanosheet molecular weight.