The Royal Microscopical Society defines:
1) Microphotography - "Photography, especially of documents, arranged to produce small images which cannot be studied without magnification. Not to be confused with photomicrography."
2) Photomicrography - "The recording by photography of an image formed by
a microscope; i.e. photography through a microscope. Note: Not to be confused with microphotography."
The 19th century microscopists in Victorian England didn't 'miss a trick' when the new technique of photography was announced. Soon after the silver halide based photographic emulsion had been developed, these microscopists had started to use their microscopes to produce microphotographs ie tiny photographs on a microscope slide.
It's a neat idea .... if you can use a microscope to magnify tiny objects so that the eye could observe them, why not use the optics of the microscope in reverse to project an image of say a painting through the microscope to create a tiny image on a microscope slide. If the slide had been pre-treated with photographic emulsion and developed like a photograph, 'hey presto' you have a permanent microphotograph of the painting which can only be viewed under a microscope. What better novelty to impress your friends with at the next meeting of amateur microscopists ... and this is exactly what many of the early microphotographic slides were used for, as microscopy was a popular past-time with Victorian 'society'.
The Victorian microscopist's used this technique to prepare a wide variety of photomicrographs including works of art, portraits of famous people and landscapes. To ensure the final image on the slide was a 'positive' the usual technique was to take a normal photograph of the subject and shine light through the developed negative, a glass plate in those days, down the microscope to create a 'positive' image on the slide, which was typically 1mm square.