The idea of subatomic worlds within worlds, as scientist Kalla Kopak phrases it in the comic-strips below, wasn't a common idea in science fiction, but it certainly is a fascinating one. The concept was explored, most notably, three times before in the world of science fiction:
The Diamond Lens, by Fitz-James O'Brien, 1858. A man peers through an incredibly powerful microscope, and discovers another world. The link goes to the Project Gutenberg text.
The Girl in the Golden Atom, by Ray Cummings, 1922. The link is to the full text of the novel at Project Gutenberg. Cummings' hero goes a step farther than O'Brien's protagonist, and actually enters into the world he discovers in a wedding ring.
Colussus, by Donald Wandrei, 1934. Wandrei's work is still in copyright, but the short story "Colussus" has been anthologized several times. Isaac Asimov's terrific book "Before the Golden Age" reprints the story, but the link here is to a recent anthology focusing solely on Donald Wandrei's work.