This presentation is composed of two parts: the first one is devoted to the rheology of thin liquid polymer films, the second one deals with the development of novel flexible stamps for imprinting of micro- and nano-structures. Thin films are ubiquitous, and they are used in a large number of technological applications. An understanding of their properties, and of the factors influencing their stability is therefore important. In particular, the rheological properties of thin liquid films, and the role played by interactions at the solid/liquid interface have been subject to much debate in recent years. A new experimental set-up was built to study the destabilization process of a thin liquid polymer film subject to an electric field. The measurement of the characteristic time of destabilization of thin liquid films of polystyrene on a solid substrate provides a way to measure the viscosity of the liquid layer. The measurement of the growth rate of an instability with sub-nanometer resolution gives complementary information about the hydrodynamics of the liquid film. The results of this work lead us to propose a model for the disentanglement of large macromolecules during the formation of the thin film by spin-coating. The last part of the presentation deals with the development of a new type of flexible organic molds for nanoimprinting. I show that patterning of polymer surfaces can be performed with high resolution (~10 nm) and at relatively low cost using these new molds. They also solve a number of problems often encountered with conventional inorganic materials which makes them easier to use and better suited to pattern large areas. I finally demonstrate applications of these molds to build a stretchable laser, and to manufacture thin transparent microstructured surfaces to study insect adhesion.