It is called the TeraDisk and it is really small, like a ordinary CD/DVD. But it's really huge in terms of space. 1 TB (1000 GB). How can this be done? The process is easy (or not). All existing optical media record data on semitransparent layers. A regular CD has 1 layer and a Blu-Ray disk has up to 8. The reason nobody can add more layers on a regular CD/DVD/Blu-Ray disk is because when the light passes through these layers it becomes distorted and by the time it reaches the final layers it becomes almost impossible to read/write on the disk.
TeraDisk achieved the 1TB limit by using 200 layers, each storing 5GB of data. So basically the data support stay the same (TeraDisk will be made out of the same plexiglas like material used in other disks) but the write/read laser technology is completely new. They say it's going to be cheap and it will be available for the public in 2010.
For more info on how this is done click the link