See the Category: 127 film.
The 127 film is a paperbacked rollfilm, 4cm wide, originally designed to store eight pictures in 4x6.5cm format. It was created by Kodak for their Vest Pocket model, and the first generations of 127 film cameras were similar folders. See Category: 4x6.5.
In 1930, during the Great Depression, the camera makers tried to optimize the use of film, and cameras began to appear taking 16 exposures in 3x4cm format on the 127 film, the first one being the Zeiss Ikon Kolibri. See Category: 3x4.
At last in the 1950s there was a short revival of the 127 film with cameras designed to take 12 exposures in 4x4cm format. The film was available in color slide emulsions, and the resulting 4x4cm slides could be projected in a normal projector designed for 24x36cm slides. They were advertised as Superslide. Kodak made such a range of very basic cameras. Rollei made a more advanced Rolleiflex Baby camera until the beginning of the 1960s. See Category: 4x4.
After the 1960s, the 127 film fell into decay. Today Kodak has stopped its production. The last factory making 127 film is Efke in Croatia, and it is still available for sale online.