Data storage using the scanning tunneling microscope has come one step nearer. Instead of using changes in surface morphology for recording as previously proposed, changes in tunneling current are produced by locally induced phase transitions between crystalline and glassy forms of a vanadate composite material. This has the advantages of being reversible, a room-temperature technique, and less susceptible to defects. The recording mechanism is thought to be the pulse-voltage-induced migration of sodium ions along the electric Field.