A group of scientists involved in ‘The Human Document Project’ are experimenting with QR Codes for very long term optical data storage. The scientist are interested in how data about the human race can be stored for millions of years and outlast the human race itself. Current optical data storage deteriorates after only a few decades but by creating QR Codes with one material embedded within another they believe they can extend this to a million years and beyond. The images below show show a centimeter sized QR Code with each pixel of the code consisting of a set of much smaller QR Codes with pixels of only a few micrometers in size. The full paper is here (PDF).