Researchers used a nanostructured glass disc as a medium, and essentially etched data “in three layers of nanostructured dots separated by five micrometers (one millionth of a meter).”

According to that same announcement, “The self-assembled nanostructures change the way light travels through glass, modifying polarization of light that can then be read by combination of optical microscope and a polarizer, similar to that found in Polaroid sunglasses. The information encoding is realized in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures.”

Most reports compared it to the famous crystals from the Superman mythos: the ones that stored the entire history of Superman’s planet within a few ounces of crystal space.

That’s an apt comparison, most notably because those crystals, sent off with young Superman before his planet was destroyed, outlived his entire species, preserving a record of their existence long after they disappeared from the universe.