I suppose that either you are sticking with the original definition of matter or you are many, many centuries out of date. The atom, as originally proposed, was an indivisible unit. BTW, we still can't "see" atoms, we can see instrument renderings which may or may not be truly representative of "atoms". We construct instruments based on looking for something we already have a conception of (to prove it true) and should not be surprised to find that they confirm that conception (they're doing what we designed them to do, finding what we designed them to find).
It still doesn't change by argument, BTW.