It's a spectacular achievement. I was pretty blown away when I discovered they could just print DNA.

But that’s only part of the solution. First was getting from DNA to RNA (meaning the packet only had to get into the cytoplasm, not the nucleus itself — and obviating any danger that the host DNA might be changed)

Another part is replacing one of the nucleobases, uracil (U) with pseudouridylyl so a recipient's innate immune system would not react to it before it got into a cell (but a cell’s protein-assembler would treat it as U). See here for a good description, plus a photo of that cool DNA-printer.

Then there’s the issue of keeping the mRNA package together until it gets to a recipient cell, protecting it from the enzymes in plasma. Enter nanoparticles, good explanation here.

Back in 1986, K. Eric Drexler predicted nanotech being useful for something like this, plus a global electronic way for researchers to work together (i.e. the Internet) in his Engines of Creation**.

So what we’re seeing is the confluence of two lines of development at least forty years in the making.

**I have to admit I was more interested in his predictions of nano-diamond layers (even in the mid 80s it was clear that Moore’s law was about to run into a heat-dissipation wall — and diamond is a really good thermal conductor). I was already working on global-communication solutions (what has become ‘the Internet’) so that was of interest, but more of an ‘of course — eventually’. Gotta admit, that happened much faster than I then thought it would.