The two phases of GST, amorphous and crystalline, also reflect light differently, allowing the surface of a DVD to be read by tiny laser.

While GST has been used for some time, the precise mechanics of its ability to switch from one state to another have remained something of a mystery because it happens in nanoseconds once the material is heated.

To solve this mystery, Xu and his research team used the pressure from diamond tools to cause the change to occur more slowly.

The team used a method known as X-ray diffraction, along with a computer simulation, to document what was happening to the material at the atomic level. By recording the changes in "slow motion," the researchers found that they could actually tune the electrical resistivity of the material during the time between its change from amorphous to crystalline form.

"Instead of going from black to white, it's like finding shades or a shade of gray in between," said En Ma, a professor of materials science and engineering, and a co-author of the PNAS paper. "By having a wide range of resistance, you can have a lot more control. If you have multiple states, you can store a lot more data."