Layer-by-layer (LbL) assembly@footnote 1@ is an easy to use method for the fabrication of multi-composite films and has kindled widespread interest in such nanohybrids.@footnote 1-@footnote 7@. Electrostatic interactions between anionic and cationic compounds (synthetic or natural polyelectrolytes, DNA or proteins) offer four major advantages: (1) layer-by-layer construction due to surface charge reversal in each layer (2) restriction to single layers due to repulsion between last layer and excess material (3) low steric demand for interaction between oppositely charged ions (4) deposition on almost any solvent accessible surface. As an introduction to the LbL-technique, the guiding principles of multilayer assembly will be presented and details of the film structure will be discussed. Since the technique allows to interface a wide variety of materials with predefined spatial arrangement, it has successfully been introduced to both materials science and applied bio-sciences. At this meeting we will focus on work relevant for surfaces in contact with biological materials or environments. This will include work on films composed of natural or semi-synthetic polyions such as charged polypeptides or polysaccharides some of which has been carried out in close collaboration with the groups of P. Schaaf (ICS) and J.-C. Voegel (INSERM U 424). @FootnoteText@ @footnote 1@ Decher, G., in: Comprehensive Supramolecular Chemistry, Vol. 9, (Sauvage, J.-P. and Hosseini, M. W., Eds.), Pergamon Press: Oxford, 1996; 507-528.@footnote 2@ Knoll, W., Curr. Opinion in Coll. & Interface Sci. 1996, 1, 137-143.@footnote 3@ Decher, G., Science 1997, 277, 1232-1237.@footnote 4@ Laschewsky, A., Europ. Chem. Chronicle 1997, 2, 13-24.@footnote 5@ Decher, G. et al., Curr. Opinion Coll. & Interf. Sci. 1998, 3, 32-39.@footnote 6@ Bertrand, P. et al., Macromol. Rapid. Commun. 2000, 21, 319-348.@footnote 7@Hammond, P. T., Curr. Opinion Coll. & Interf. Sci. 2000, 4, 430-442.