Take a square, cut it into nine smaller copies of itself. Take the middle one out and fill the others with nine smaller copies of themselves each. Repeat the process until language gives way and you end up with the image above.
I quote from Wikipedia: Mobile phone and WiFi fractal antennas have been produced in the form of few iterations of the Sierpinski carpet. Due to their self-similarity and scale invariance, they easily accommodate multiple frequencies. They are also easy to fabricate and smaller than conventional antennas of similar performance, thus being optimal for pocket-sized mobile phones.
Who, in the world, had this idea?!
What does it take to geek out about Sierpinski carpets: Self-similar mobile phone antennas. That’s what!