Imagine you have a delicious pizza pie in front of you. Now, no matter how big or small that pizza is, if you measure around it (the circumference) and across it (the diameter), the ratio will always be the same. That special number is what we call 'pi'. Pi is an extraordinary number with a long and mystical history. It's an 'irrational' number, which means it goes on and on without repeating, just like the exciting adventures in your favorite book. The first few digits are 3.14, but scientists have calculated pi to over a staggering trillion digits! In the ancient world, mathematicians knew about pi. The Egyptians and Babylonians had approximations for the number, and the ancient Greek mathematician Archimedes is famous for his method of calculating it more accurately. Now, here's a fun fact: Every year on March 14th, mathematicians and pie lovers around the world celebrate 'Pi Day.' Why? Because the date format in America is 3/14, which is the approximate value of pi! Isn't it amazing how a simple number can hold so much history, mystery, and pizza?