In the books All Shapes and Sizes and Savage Shapes you see how to make Penrose tiles which were invented by Roger Penrose - one of our maths heroes!
If you look at a patterned wallpaper, you'll see that
the same pattern keeps coming up over and over again but...
... the clever bit about the Penrose tiles is that you can put them together to cover an area, but even if you go on forever the pattern never will exactly repeat itself!