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We demonstrate that a scanning tunneling microscope can be used to obtain structural information on membrane proteins in their natural environment and of isolated protein molecules deposited on graphite. We focused on ion channel forming proteins, i.e., gramicidin and the nicotinic acetylcholine receptor. The latter is a well described membrane channel in the neuromuscular synapse. To get more than topological information we developed a fast and stable method to characterize the changes of the current/voltage curvature while scanning over a sample. This results in a material‐dependent image color which is also sensitive to variations of chemical structure inside the molecule. The method was first tested with liquid crystals on graphite clearly showing their atomic structure in the STM image. In a second step the method was applied to obtain structural information about gramicidin adsorbed on graphite.