A researcher setting up an atomic force microscope (AFM), ready for use. A binocular light microscope is used to ensure that the AFM probe is in the correct starting place on the sample. The AFM is capable of atomic-scale resolution, and works by drawing a very fine 'stylus' across the surface of the sample. A carefully-balanced spring ensures that the tip follows the contours of the sample, enabling a map to be constructed of its surface. The AFM is similar in concept to the slightly more powerful scanning tunnelling microscope (STM), but has the advantage that it may be used with non- conductive samples such as biological specimens.