This is very cool. From way back in 1971 a professor Leon Chua at the University of California (Berkeley) wrote a paper describing four basic passive electrical components: resistors, capacitors, inductors, and memristors. Until this year, the last one of these was only theoretical in nature, but some bright folks have finally cracked it.

Basically, its a substrate that exhibits a permanent(?) resistance change due to past current history. You could use them to make extremely fast, dense solid state storage devices.

Memristors, they exist!