Résumé
Biological membranes are currently modeled as two-dimensional structures essentially composed of lipids and proteins organized in domains. Topographical images of eukaryotic, prokaryotic, plant cell surfaces, and isolated membranes were published and revealed structural details that could not be detected by other approaches, thus presenting the atomic force microscope (AFM) as a potent additional tool for the biologist. The principle of the AFM that consists in raster scanning a surface with a tip of finite size imposes constraints on the type of material that can be examined. For instance, the AFM does not perform imaging of cells in suspension. Because of the very soft nature of biological material, particular attention must also be paid to the sample preparation and also the adjustment of experimental conditions. This chapter presents a practical basis for the imaging of cells and membranes by the AFM. The essential difference between the physicochemical and the biological applications of the AFM is the constraint imposed by the softness and the fragility of the samples.