In modern physics we're unable to measure things smaller than a certain size because the act of measuring will affect the thing being measured. For example, something smaller than a photon cannot be observed/measured using light, and something smaller than an electron cannot be measured using an electron microscope. There's a name for this which escapes me; hopefully someone has the name at hand and can correct me if I've mis-stated it.
This would be the modern equivalent of a single atom not being able to emit a film.