We basically can already work on the nano scale (see the nano-guitar for one famous example). The problem is that below a certain threshold you can't just "buil

We basically can already work on the nano scale (see the nano-guitar for one famous example). The problem is that below a certain threshold you can't just "build X but with tinier parts" you need to completely re-think how it interacts with stuff there's not really much room for anything but gross chemical signal processing and no conventional mechanical parts at that size. The future at that scale is basically designer viruses being pumped out by designer cells --which we are working on-- but it's not easy.