has an entertaining explanation. Chips need to become smaller if you want to speed them up. The transistors inside the chips are like buildings in a city. However, the wires that connect them play the role of the streets. The streets waste a lot of space that could be used for real estate.
The Hewlett-Packard solution is to build the streets above the buildings, not below them. Moreover, it is just the streets that appear in the first floor above the building: the perpendicular avenues are placed in another layer two stories above the buildings. ;-) There is an insulating (or "insulting", as a classic wrote) soap-like layer in between the streets and avenues that can become conductive if you apply some voltage to the avenues. The same voltage applied to the streets turns the switch off, they strangely say. Both streets and avenues are only a few atoms thick.
The immediate way to use this technology as early as in 2007 are FPGAs, modern reprogrammable chips. It is not clear whether the breakthrough may be useful for the conventional architecture of microprocessors and memory chips.