electron microscopy

This term refers to a specialized scientific methodology rather than a single piece of equipment. While the instrument used is called an electron microscope, the term microscopy describes the entire process and field of study involving the use of electron beams to visualize specimens.

As a technical term for a scientific process, it is treated as an uncountable noun. It does not have a plural form in standard usage, as it describes a category of technique rather than a discrete object.