Explore intriguing appearances of pi and the Fibonacci sequence outside of mathematics in this video from NOVA: The Great Math Mystery. Although well-known in mathematics, the numbers of the Fibonacci sequence are also frequently found in the natural world, such as in the number of petals on flowers and the number of spirals of a pinecone. Pi is commonly recognized as a number that relates a circle's circumference to its diameter but it also appears in many other phenomena. For example, pi is related to the probability that a dropped needle will cut a series of parallel lines; it also can be used to calculate the length of a meandering river.