In 1202, Leonardo Fibonacci described a special series of numbers. This series has come to be known as the Fibonacci series, which looks as follows: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, et cetera.
The next number may be formed by adding up two successive numbers.
In 1611, the astronomer Johannes Kepler discovered something special about the Fibonacci series. If you divide a number from the Fibonacci series by the preceding number from that series, the outcome will approach the golden ratio number phi. That the outcome always approaches the number 1.618 is a surprising property.