About fractal geometry.
My nephew is 9 and home schooled and probably a little genius. He just learned about fractals from some materials his mom picked up. My mom went to florist school, but has always loved to think about things like Flatland, which is a novel set in just two dimensions. And me - well, I loved math in high school but I think I've forgotten most of it. I do remember I loved Fibonacci numbers. All I remember about Fibonacci numbers now is how they start, and that they had something to do with spirals.
My mom and I just watched an old video my sister-in-law loaned us about fractal geometry that featured Stephen Hawking and a very natty Arthur C. Clarke (attired in some sort of safari jacket/shirt cross) discussing the wonders of fractals.
Never say my family doesn't know how to have fun.