You can't see them, but most of the metals around you—coins, silverware, even the steel beams holding up buildings and overpasses—are made up of tiny metal grains. Under a powerful enough microscope, you can see interlocking crystals that look like a granite countertop.

It's long been known by materials scientists that metals get stronger as the size of the making up the get smaller—up to a point. If the grains are smaller than 10 nanometers in diameter the materials are weaker because, it was thought, they slide past each other like sand sliding down a dune. The of metals had a limit.

But experiments led by former University of Utah postdoctoral scholar Xiaoling Zhou, now at Princeton University, associate professor of geology Lowell Miyagi, and Bin Chen at the Center for High Pressure Science and Technology Advanced Research in Shanghai, China, show that that's not always the case—in samples of nickel with grain diameters as small as 3 nanometers, and under high pressures, the strength of the samples continued to increase with smaller grain sizes.

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