Nanochip Inc. has developed prototype arrays of atomic-force probes, tiny instruments used to read and write information at the molecular level and hopes to offer its first product by mid-2007. These arrays can record up to one terabit in a single square inch.

That’s the storage density that magnetic hard disk drive makers hope to achieve by 2010. It’s roughly equivalent to putting the contents of 25 DVDs on a chip the size of a postage stamp.

Imagine, for instance, recording dozens of hours of high-quality digital video on your mobile phone or storing your entire digital music collection your PDA.