I am trying to identify a story where a man drinks a potion of dark matter that makes him increasing smaller so that he slips through atoms and sees universes in them. Story/stories probably between 50's to 70's, probably magazines. I'm reading a non-English adaptation and want to identify source.
On the off chance that you're mistaking the method used to start shrinking, this question holds two separate answers involving a person shrinking until they start seeing universe between atoms. "He Who Shrank" is a 1936 story by Henry Hasse about a scientist's assistant who gets injected by his scientist metaphor with his "Shrinx" formula and he becomes so small that he is huge in another universe and then continues shrinking until he winds up at Earth.
"Submicroscopic" involves a shrinking machine with the scientist finding a beautiful princess in one of the worls within atoms. The Girl in the Golden Atom involves "a young chemist who finds a hidden atomic world within his mother’s wedding ring". :) It's a fairly common trope in science fiction.