Have you ever seen an hologram? No? Now you can see them and also make them.
Here’s an AOL guy who has managed to mount an hologram-generator system from a PIN diode. You can see some photos (2D, of course)
There are some other sites talking ’bout holography: drawn by hand, creating different types of holograms, The Holography Book, Google’s directory and Holoworld (by the creator of diode’s holography).
Of course, you can also look at Slashdot‘s discussion on this topic.