In characterizing materials, especially live biological specimen such as cells, it is important not only to be able to explore the surface but also any subsurface structures and properties - without damaging or destroying the sample and for hard and soft materials alike. For example, many synthesized nanoparticles can readily get inside a cell. Therefore studying the cell surface, while useful, can provide little or no knowledge about the particles hidden in the interior of the cell. Another example is the detection of nanoscale defects in nanofabricated structures such as those made by electron beam lithography; or the detection of embedded cracks and voids in nanocomposite materials. Researchers have now shown that an atomic force microscope can obtain a range of surface and subsurface information by making use of the nonlinear nanomechanical coupling between the probe and the sample.