> Tiny self-replicating machines which produce other things to atomic precision

Don't expect it to happen soon - we can't even make big self-replicating machines yet.

We don't even know what machines would look like at such a small scale. Structures behave very differently than they do at human scale; fundamental components like ropes, gears and pulleys might not be possible.

And then there's the problem of programming these machines; you can't exactly put an AVR inside them.