QR code measuring 1.98 μm^2, requiring electron microscope to be read, can preserve data for centuries/ millennia

https://www.eurekalert.org/news-releases/1116677

"individual pixels 49 nm... code milled into thin ceramic films using focused ion beams, ensuring chemically/ physically stable long-term data storage unlike magnetic and electronic media/ hard drives lasting only a few years... requires no energy/ cooling to maintain data once written... single A4 sheet could theoretically hold over 2 terabytes... data centers... future: increasing writing speeds and developing scalable manufacturing processes for more complex data structures"