In this review article we discuss the thin film analytical techniques of interface sensitive X-ray and neutron scattering applied to aligned stacks of amphiphilic bilayers, in particular phospholipid membranes in the fluid L(alpha) phase. We briefly discuss how the structure, composition, fluctuations and interactions in lipid or synthetic membranes can be studied by modern surface sensitive scattering techniques, using X-rays or neutrons as a probe. These techniques offer an in-situ approach to study lipid bilayer systems in different environments over length scales extending from micrometer to nanometer, both with and without additional membrane-active molecules such as amphiphilic peptides or membrane proteins.