Plastic As Strong As Steel?

What does this pearl and plastic as strong as steel have in common? They are made by a series of very thin layers. Let me explain.
Researchers at University of Michigan have come up with a way to make plastic that's almost as strong as steel. Plastic that could, with a little more development, be used for lighter, stronger armor for police or military use. Among other things, of course.
How do they make it? Using a series of layers of clay nanosheets and a glue-like polymer. Nanosheets are fairly strong at a microscopic level, but if you try and make something bigger, that strength just doesn't transfer. Using nanosheets in a series of layers seems to make them very strong.
It's very similar to how a pearl is made: through a series of very thin layers.
Via Slashdot