Recent progress in submolecular-level structural investigations of planar lipid model membranes using scattering techniques is reviewed. Particular emphasis is placed on the quantification of peptide/lipid and protein/lipid interactions. Floating phospholipid monolayers on aqueous subphases (“Langmuir monolayers”) enable full physicochemical control of a membrane mimic, thus providing unique opportunities for investigations of the interaction of peptides with biomembrane surfaces. Particular progress has been recently made with surface-sensitive diffraction methods for characterizing molecularly thin protein crystal sheets. We describe (multi-) bilayer systems for which the distribution of submolecular fragments has been determined, providing a fully resolved picture of their thermally disordered structure using the “liquid-crystallography” approach of White and co-workers. This approach has recently been extended to tackle basic problems of membrane protein folding. Applied to solid-state interfaces with a fluid or gas phase, scattering methods provide invaluable tools for the Ångstrom-scale characterization of systems as diverse as uniaxially oriented proteins in molecular layers attached to self-assembled monolayers (SAMs), hybrid bilayer membranes (HBMs), and polymer-cushioned, tethered bilayer membranes.