Scanning probe microscopes using nanometer-scale probes enable imaging of materials with spatial resolution on the order of atoms. The most popular scanning probe techniques, including scanning tunneling microscopy (STM), scanning near-field optical microscopy (SNOM), and atomic force microscopy (AFM), can be used to measure the topographical, electrical, optical, and mechanical properties of materials in environments including vacuum, air, and water. High spatial resolution is achieved by confining interactions between the probe and sample surface to the nanometer-scale dimensions of the probe itself. As a result of their unique imaging and measurement capabilities, scanning probe microscopes using nanometer-scale probes have become essential for high-resolution characterization of biomaterials and biological molecules.