Scanning Probe Microscopy is a technique that allows scientists to study materials at a very small scale by using a physical probe to scan the surface of the material. Synonyms for this technique include Scanning Tunneling Microscopy, Atomic Force Microscopy, and Near-field Scanning Optical Microscopy. Scanning Tunneling Microscopy uses an electrically conductive probe to scan the surface of a material and detect variations in the electrical resistance. Atomic Force Microscopy uses a micro-fabricated cantilever fitted with a sharp tip to scan the surface of a material. Near-field Scanning Optical Microscopy uses a probe to scan the surface of a material while simultaneously illuminating it with a laser, allowing researchers to study the material's properties with high spatial resolution.