Scanning probe microscopy (SPM) was originally conceived as a method for measuring
atomic-scale surface topography. Over the last two decades, it has blossomed into an
array of techniques that can be used to obtain a rich variety of information about
nanoscale material properties. With the exception of friction measurements, these
techniques have traditionally depended on tip–sample interactions directed normal to
the sample’s surface. Recently, researchers have explored several effects arising from
interactions parallel to surfaces, usually by deliberately applying a modulated lateral
displacement. In fact, some parallel motion is ubiquitous to cantilever-based SPM, due to
the tilt of the cantilever. Recent studies, performed in contact, noncontact, and
intermittent-contact modes, provide new insights into properties such as structural
anisotropy, lateral interactions with surface features, nanoscale shear stress and contact
mechanics, and in-plane energy dissipation. The understanding gained from interpreting
this behavior has consequences for all cantilever-based scanning probe microscopies.