The Eiffel Tower is over twice that height but weighs just five and half kilotons–some 10 times lighter. The difference, according to materials scientist Julia Greer, is that “elements of architecture” were introduced into the design that allowed it to be stronger and more lightweight while using far less materials. Where the pyramids are four solid walls, the Eiffel Tower is more skeletal in structure–and vastly more efficient as a result.

Today, in her lab at Caltech, Greer is trying to make the same sort of leap on a nano scale, engineering hollow materials that are fantastically lightweight while remaining every bit as stiff and strong as existing versions. The applications for this “hierarchical design” are myriad, but its impact could be profound.