Sub Miniature Photography
If you are using a very small camera to take your photographs you are engaging in subminiature photography. There are no set guidelines on what a small camera is and what a subminiature model is and it is often up for debate among photographers.
Generally cameras that are smaller than a small format 135 or 828 roll film camera are included. Cameras that can produce a film image smaller than the standard 135 format (24x36mm) are also usually termed subminiature. True subminiature cameras are very small, precision instruments. They often have more in common with a watch than a camera. Because they are so small in size and weight they can easily be carried in your purse or pocket and are very accessible.
There are also cameras that are pretty easy to conceal and are often used in surveillance or intelligence operations. Subminiature cameras and film are still available, but the age of small digital cameras has severely dented their sales and usage.