Through-silicon vias (TSVs) are the standard way to stack chips these days. They’re basically micrometer-scale vertical wires embedded in a sliver of silicon that link one chip, such as a processor, to another, such as a memory chip, stacked atop the first. That way signals don’t have to travel very far between the two chips. Done right, they should save time, energy, and space. But, at the moment, they don’t add any intelligence.

Engineers in Germany want to change that by making TSVs smart. Their answer is a “through-silicon transistor,” and if they’re right, it should let designers actively control which signals are allowed to go from one chip to another. The implications aren’t just more intelligent control of the flow of information—through-silicon transistors could also keep sensitive chip designs safe from prying (electron-microscope enhanced) eyes.