A discussion is provided of the widening use of atomic force microscopy (AFM), which goes beyond biological applications from topographical strategies and enters the realm of protein and biological sample characterization. AFM is still a robust technique for imaging surface topography with subangstrom vertical and subnanometer lateral resolutions. It can be used to monitor always-changing events in response to various stimuli through exchange of buffer compositions in situ, including processes for controlled flow-through experimentation. As used in virology, AFM provides information not easily available from conventional x-ray crystallography and electron microscopy. AFMs have also been used to study intra- and intermolecular forces. AFMs can very accurately measure the cantilever's response to force. When the spring constant is calibrated, deflection can be expressed in units of force. For unfolding proteins, a research group at the University of Technology in Dresden, Germany, has unfolded individual protein molecules in intact membranes by moving a microscope until it contacts a membrane. They then retracted it, and in some instances, just one molecule attached to the tip through a non-specific mechanism and unfolded on retraction. The scientists have discovered that membrane proteins assemble in a two-stage process. The researchers can functionalize the cantilever tip by coating it with a molecule of interest and then put the tip in contact with the sample and pull it away. After various other steps are completed, the result is a plot of force versus distance. Various other experiments are described in which biological sample characterization is being explored.