I saw this movie in the theater. It had something to do with transforming life size humans into smaller size, around the size of a Barbie or G.I. Joe. And if the procedure was done correctly the smaller sized human would be deformed. I saw this movie around 1968-1969. But it could have been older. It looked like it was in the fifty’s, but was in color.
Check out Wild Wild Planet (1965)
Maybe Dr. Cyclops?
https://www.imdb.com/title/tt0032412/?ref_=fn_al_tt_1