The format of the negative is the defining characteristic of subminiature cameras as used here. The size of the camera is not the determining factor, though in most cases these cameras are some of the smallest ever produced. Minox, 16mm, disc, and half-frame cameras. The majority of these cameras are not toys. In fact, many of them have some of the more advanced optics of their time, as well as being mechanical marvels.
Many older models rival the better lenses produced today.
Cameras produced fifty years ago are carried daily in the pockets of many professional photographers.