There are a few things that come to mind but I think one of the biggest breakthroughs was in photography. And I don’t mean digital cameras but the ones with the photographic films before those. Those photographic films had silver halide nanoparticles on them and the size and shape of those particles determined the resolution of the image. With this technology we were suddenly able to capture everything that was going on in the world and keep it for future generations.
Of course, modern microchips are also nanotechnology so without it we wouldn’t have smartphones so this is also a major advancement.
I think the biggest recent break through are all the 2 dimensional materials. Graphene, BN, MoS2, etc. Until recently we thought materials like this couldn’t exist in isolation, they would be too unstable. But now they are everywhere in research. Whole week long conferences are devoted just to 2D materials. It’s very exciting.
But the nanoworld has been around for as long as the planet has. Nanoparticles of carbon are found in ordinary chimney soot. It’s just now we have the support technology to be able to look at them, manipulate them and examine them in all sorts of ways.