For most of the history of RNA research, the molecule's therapeutic promise was undermined by a fundamental problem: RNA is unstable, immunogenic, and unable to cross cell membranes on its own. You could design a sequence that encoded exactly the right protein, synthesise it cleanly — and watch it degrade before reaching its target. The biology was understood; the delivery was the bottleneck. Lipid nanoparticles solved that problem. Not all at once, and not simply — but the arc of LNP development over six decades produced the delivery technology that made RNA therapeutics clinically viable. The mRNA vaccines of 2020–2021 were the most visible expression of that achievement. They were not, however, the end of the story. They were the proof of concept that opened the pipeline.