Paras Prasad, a chemist at the State University of New York at Buffalo, has developed a technology for squeezing a thousand times more data onto a compact disc. Prasad dopes a polymer with a fluorescent dye that emits light when illuminated by a weak laser beam--but when blasted with an intense laser, it loses much of its fluorescence. That means Prasad can write dark bits of information on a disc with a narrowly focused, high- intensity laser and later read them with a weak one. Because he can focus his lasers to a precise depth, he can stack many layers of data onto a single disc.