Im assuming you mean your Prusa can print a solid 1mm cube with rounded edges, which is very different than a lattice structure with an overall 1mm size
I wish I had a 4000 lasers plaid-mode FDM printer able to work in titanium, PLA, ASA, styrofoam, carbon nanotubes, steel, copper, wood, concrete, borosilicate, and EPDM at micrometers.