Scanning tunnelling microscope, 1980s. This is an example of the pioneering equipment used in the 1980s to probe the surface and structure of materials. It was built at the Physical Measurement Laboratory (PML) of the National Institute of Standards and Technology (NIST). Built in 1984, this was one of the first STMs available in the USA, following on from the first one built at IBM Zurich in Europe. It is one of the earliest surviving examples of an STM. An STM uses an atom-tipped probe to build three-dimensional atomic-scale maps of surface structures. Photographed in 2019, on display at NIST's Advanced Measurement Laboratory (AML), Gaithersburg, Maryland, USA.