Phospholipid bilayers are used in biochemistry as model systems for biomembranes. Proteins and other biomacromolecules can be adsorbed to and inserted in these layers to study their biological function. Using Atomic Force Microscopy, we found that incorporation of certain synthetic transmembrane peptides transforms the bilayer to a striped phase. Depending on the nature of the peptide, straight or meandering bundles of parallel stripes at distances of 8 nm may appear. Here, we present a first molecular scale model to unravel the generic properties of the peptides and phospholipids which generate striped phases. This opens a window to produce striped phases in other materials as well. (C) 2002 Elsevier Science B.V. All rights reserved.