field-i|on microscope «FEELD Y on, -uhn»,
an extremely powerful microscope similar to the field-emission microscope but using, instead of electrons, the ions of a gas near the emitting surface to produce a magnified image of the emitting surface on a flourescent screen; ion microscope: »
In the field-ion microscope, it is possible not only to observe the positions of individual atoms on a metal surface at low temperatures, but also to follow the movement of the atoms when the specimen is heated (New Scientist).
Useful english dictionary. 2012.