Technically we already can go from human scale to nano or even atomic scale in "one operation". i.e. a scanning tunneling microscope you etch a tungsten wire in acid and then can go and look at individual carbon atoms at room temperature.

An atomic force microscope is even more direct - while not absolutely "atomic" - you can definitely with a sharp enough tip push things around on the nanoscale.

The problem is definitely as you note: things do in fact behave very differently when you're doing that.