GE just announced that they're fitting 500GB of data on discs the size of DVDs through "holographic storage" technologies. It's OK to be a bit lost. This clip explains the idea in more tactile terms.
While CDs are read in 2D space (one layer), and DVDs are read in much the same way (but with an extra layer+ of data), GE's holographic storage uses the entire disc density for storage. Data drawn through chemical reactions floats if suspended in gelatin.
Or...you could let the expert explain it in his own words about a minute in to this clip...Mr. Fancy Goggles and his fancy blue shirt. [via boingboing]