The first commercial SEM was produced by the Cambridge Instrument Company and became available in 1965.
In 1923, Busch demonstrated that a beam of electrons could be focused by magnetic or electric fields. This opened the way for the development and construction of the first TEM in 1932, by Knoll and Ruska, and the first SEM in 1938 by M. von Ardenne. Zworykin et al. (1942) produced an SEM with a potential resolution of 50 nm. These early SEMs had little better than LM performance. Great improvements in the design, particularly in the area of detection and the use of SE were made by O.W. Oatley and his group at Cambridge University. McMullan (1953) constructed a prototype SEM in the Cambridge Laboratories and by 1955 development had achieved a resolution of 25 nm. The first commercial SEM was produced by the Cambridge Instrument Company and became available in 1965 with a resolution of about 20-25 nm.
Since then, the SEM has evolved to become one of the most versatile tools of the physical and biological sciences. Today, many SEMs are commercially available and they all contain the same essential features: an electron optical column in which an electron beam is generated under high vacuum, and focussed to a tiny spot on the specimen surface. The specimen response is detected and then displayed in visual mode.