Shrinky Dinks are awesome. Color some strips of plastic, pop 'em in the oven and watch them fold up onto themselves. It turns out that these rainy day items are made from the same polymer as Styrofoam cups: polystyrene. Polystyrene, which was first commercialized in Germany in 1931 (styrofoam wasn't developed until 1954 in the United States), is a very versatile polymer and millions of tons of it are produced annually. A Shrinky Dink starts out as a sheet of polystyrene that has been pressed and flattened while close to the melting point. This forces the polymer chains to stretch out and line up. The sheet cools and the polymer chains are frozen into place (think of it as stretching out a Slinky and holding it). When you throw a Shrinky Dink in the oven, the polymer sheet warms up, and the polymer chains start to move around. When hot enough, all of the polymer chains coil back up, making the sheet of polymer shrink, just like a Slinky will pull itself together when you let go. Scientists at Northwestern University recently took advantage of that property to create nanopatterned surfaces. To get structures really, really close together, they used the stretched polystyrene and printed dots on the surface. Then they heated up the sheet, which shrunk, creating a very high-density array of dots.