SPM is a subfield of microscopy that uses a physical probe to scan the specimen to create pictures of surfaces. The scanning tunnelling microscope, a tool for atomic-scale surface imaging, was developed in 1981, the same year that SPM was established. Heinrich Rohrer and Gerd Binnig carried out the first successful scanning tunnelling microscope experiment. Their ability to control the gap distance between the sample and the probe by means of a feedback loop was crucial to their success. Multiple interactions can be imaged at once using many scanning probe microscopes. A mode is the term used to describe the process of leveraging these interactions to produce a picture. Some probing techniques achieve a remarkable atomic resolution, albeit the resolution varies slightly amongst approaches. This is primarily because piezoelectric actuators can carry out motions with an atomic-level level of precision and accuracy when given an electronic command. This group of methods is referred to as "piezoelectric methods". The data are typically obtained as a two-dimensional grid of data points, which is then displayed as a computer image in false color. This is the other thing that unites all the data.