8mm is a small format film, invented by Kodak in the 1930s as a lower cost home-movie alternative to the 16mm.

Though identified by it's frame width as 8mm, the original incarnation of the format would actually use a 16mm film spool that users would expose only half the width of the film, then flip it over to expose the remaining 8 millimetres for additional footage. When originally processed the 16mm film would be split down the middle reducing the final product to an 8mm strip. You might find this in your collection as a Double 8.

Later, the 8mm would evolve into the cartridge based Super 8, and eventually supporting the inclusion of sound on the films via. magnetic strips that can be found along the edges of the frames. The ease of use, due to the effortless handling of the film, made the format a popular choice for average consumers and amateur film makers alike.