A 1.98-square-micrometer QR code, etched into ceramic thin film and verified by Guinness, showcases a new approach to ultra-dense, long-term data storage. How small can a QR code actually be?

For those of us who weren't paying attention, over the last few years, scientists around the world have been one-upping each other in a bid to create the smallest QR code that can be reliably read.