typical phase behavior of a Langmuir monolayer at the airwater interface. During the transfer of DPPC with a low surface density from the air/water interface onto a solid substrate, regular stripe patterns can be formed. The resulting stripe patterns are composed of DPPC molecules in the low density liquid expanded (LE) phase in the channels and DPPC molecules in the higher density liquid condensed (LC) phase in the stripes, respectively, as illuminated in the sketch of Figure 1 e. The formation of stripes horizontal with respect to the threephase contact line was attributed to the substrate-mediated phase transition while vertical stripes were formed due to a secondary transversal instability of the monolayer, similar to the Rayleigh instability of liquid ridges. [ 7 ] Vertical stripes were often obtained at slightly higher surface pressures and lower transfer velocities. Using the resulting DPPC patterns, the patterning of nanocrystals and nanoparticles as well as guiding of cell growth was demonstrated. [ 8 ] Because no masks or stamps are required as for other patterning methods like photolithography or microprinting, the LB patterning has the advantages of low cost and high throughput. However, one of the major challenges for such methods employing self-assembly and self-organization is the lacking of pattern quality, refl ected by irregular structures or defects. For self-organized LB patterns formation onto fl at surfaces, irregularity is frequently observed owing to the Rayleigh instability, structural defects on the substrates or impurities on the water surface. Specifi cally in the case of the vertical DPPC stripe structures on fl at surfaces, branched patterns with a certain irregularity of the overall pattern are often obtained.Herein, we report an effective method to suppress the branching of self-organized molecular monolayer stripes obtained with the LB technique by using prestructured surfaces. Previously, prestructures were extensively used to create patterns of functional molecules and particles. [ 9 ] However, less attention has been paid to improve the pattern quality of self-assembly and self-organization patterning. Our concept is to use prestructures to introduce a spatially periodic forcing, where certain properties of the substrate (such as the wettability or the strength of interaction between the monolayer and the substrate) vary with a well-defi ned spatial frequency, [ 10 ] subsequently infl uencing the self-organized DPPC patterns. With the spatial confi nement provided by the prestructures, branched structures in vertical LB can be well suppressed, leading to LB patterns with a perfectly regular periodicity and orientation. We further demonstrate that the spacing in between the prestructure lines has a signifi cant infl uence on the LB patterns, where the periodicity of the LB patterns can be adjusted according to the periodicity of the prestructures or Micro/nanoscopic surface patterning is of great importance owing to its applications in many fi elds such as electronics, optic...