I Don't Know

As best I know, it was the first widely-available way to store lots of data in a small space, just in time for a bunch of James Bond and spy movies. I used both microfilm and microfiche all the way through school.

My favorite spy-film-related thing is that as recently as the Reagan era spy satellites literally dropped their film to Earth from orbit.

Hey, Miss C., the history of microfilm might be a good article. As I remember, it is usually an 8 x 11 black and white image reduced to the size of a 35mm slide. Smaller versions were used in a system called microfiche. I am curious how it became synonymous with spycraft.