I remember when 650 MB seemed like all the storage in the world. Back in the days when CD-ROM first appeared, it felt like that was all you would ever need. But then, of course, along came mp3s, Divx, broadband and all sorts of other stuff. Suddenly, that CD-RW drive seemed like it was always burning something, and now and again you'd find some 705MB movie or something that would just not fit on a CD. OK, DVD-RW to the rescue. Now you can store 6 or 7 movies, and thousands of mp3s, on one DVD. But how long will it be before the space afforded by DVD-RW stops being enough? Physicists at Imperial College London have described a means of encoding up to 1 TB (Terabyte) of data on a single DVD or CD. A DVD which had this kind of capacity would store 472 hours of video. Called MODS - for Multiplexed Optical Data Storage - by the Imperial College team, this format is enough to store every episode of "The Simpsons" ever made on one disk. Its enough to store the Lord of the Rings trilogy 13 times over, or all 238 episodes of Friends.