Microfilm is a way of storing documents by photographing them at a greatly reduced size onto rolls of special film. Before computers became common, libraries, newspapers, and government offices used microfilm to save space: thousands of pages could fit on a single small roll of film that you could hold in your hand.

To read microfilm, you thread the roll through a machine called a microfilm reader, which projects the tiny images onto a screen and magnifies them back to readable size. You turn a knob to scroll through the pages, searching for what you need. Many libraries still keep old newspapers and historical records on microfilm because the film can last for hundreds of years if stored properly.

The technology was especially important during World War II, when spies used microfilm to smuggle secret documents: they could photograph hundreds of pages and hide the tiny film roll in something as small as a coin. Today, most information gets stored digitally on computers, but microfilm remains valuable for preserving historical materials. Some libraries are now converting their microfilm collections to digital files, though the process takes years because someone has to scan each frame individually.