Hundreds of rectangles, each the size of a grain of rice, cover a shiny platter of silicon at a research facility belonging to Micron Technology Inc.These cells contain circuits etched at a width of 50 nanometers -- 2,000 times thinner than a human hair -- the leading edge in a shrinking process in which a single memory chip can now hold hours of music or hundreds of digital pictures.

But makers of memory chips are looking ahead to a day, not too far off, when technology based on silicon bumps up against the laws of physics and memory can't be made any smaller, with implications for gadgets like MP3 players and digital cameras.

That would slow the development of things like digital music players and cameras, for which current flash memory - used to store music and images - will not suffice beyond the next couple of years.