David Kesmodel from WSJ writes to let us know about an IBM breakthrough: a practical three-dimensional semiconductor chip that can be stacked on top of another electronic device in a vertical configuration. Chip makers have worked for years to develop ways to connect one type of chip to another vertically to reduce size and power use. The IBM technique of "through-silicon vias" offers a thousand-fold reduction in connector length and a hundred-fold increase in connector density. The new chips may appear in cellphones and other communication devices as soon as next year. PhysOrg has more details.