Holographic message encoded in simple plastic
There are many ways to store data -- digitally, on a hard disk, or using analogue storage technology, for example as a hologram. In most cases, it is technically quite complicated to create a hologram: High-precision laser technology is normally used for this.
However, if the aim is simply to store data in a physical object, then holography can be done quite easily, as has now been demonstrated at TU Wien: A 3D printer can be used to produce a panel from normal plastic in which a QR code can be stored, for example. The message is read using terahertz rays -- electromagnetic radiation that is invisible to the human eye.
A hologram is completely different from an ordinary image. In an ordinary image, each pixel has a clearly defined position. If you tear off a piece of the picture, a part of the content is lost.
In a hologram, however, the image is formed by contributions from all areas of the hologram simultaneously. If you take away a piece of the hologram, the rest can still create the complete image (albeit perhaps a blurrier version). With the hologram, the information is not stored pixel by pixel, but rather, all of the information is spread out over the whole hologram.
