What was the first bit of mathematics that made you realize that math is beautiful? (For children's book) I'm a children's book writer and illustrator, and I want to to create a book for young readers that exposes the beauty of mathematics. I recently read Paul Lockhart's essay "The Mathematician's Lament," and found that I, too, lament the uninspiring quality of my elementary math education.
I want to make a book that discredits the notion that math is merely a series of calculations, and inspires a sense of awe and genuine curiosity in young readers.
However, I myself am mathematically unsophisticated.

What was the first bit of mathematics that made you realize that math is beautiful?

For the purposes of this children's book, accessible answers would be appreciated.

For me, it was the beauty of the number 1, how it can be multiplied with anything , and it won't change the number it is being multiplied with, also how it can be represented as any number divided by itself such as 4/4=1 
I would also love to share this beautiful poem by Dave Feinberg that is titled "the square root of 3" and was also featured in a Harold and Kumar Movie, it renewed my love for math and is and always has been one of my favorite poems! :
I’m sure that I will always be 
A lonely number like root three
The three is all that’s good and right, 
Why must my three keep out of sight 
Beneath the vicious square root sign, 
I wish instead I were a nine
For nine could thwart this evil trick, 
with just some quick arithmetic
I know I’ll never see the sun, as 1.7321 
Such is my reality, a sad irrationality
When hark! What is this I see, 
Another square root of a three
As quietly co-waltzing by, 
Together now we multiply 
To form a number we prefer, 
Rejoicing as an integer
We break free from our mortal bonds 
With the wave of magic wands
Our square root signs become unglued 
Your love for me has been renewed
