Silver halide crystals are stacked in film in 3 dimensions and are themselves 3 dimensional objects. Pixels are not stacked in 3 dimensions but instead are manufactured in a 2 dimensional array on a substrate. Thus a pixel is square but one of the emulsions in Ektar 100 is a cube, and each cube is far smaller than a pixel and each cube in the film are stacked top to bottom and left to right in a random patter of billions of cubes. In fact, for every 108 mg of silver in film, there are 6.023 x 10^20 atoms of silver. There are about 300 mg of silver in ever square foot of film.
Originally Posted by Ektagraphic
Silver halide crystals come in virtually every geometric shape including cubes, octahedra, pyramids, and etc. The pAg at the time of manufacture governs the form. I describe this in my book.
The developed silver can be in the form of filaments, tablets, and a variety of other shapes depending on the developer. This is shown in Haist for example, with photomicrographs.
So in a way, yeah, films have squares! Only they are better, they are cubes.