Fibonacci number

Today, I want to introduce a mysterious progression "Fibonacci number" because I thought it is very interesting when I knew it. My mathematics teacher taught it for me last year.

"In mathematics, the Fibonacci numbers
are the numbers in the following integer
sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34,
55, 89, 144, ...

By definition, the first two Fibonacci numbers are 0 and 1, and each
subsequent number is the sum of the previous two. Some sources omit the
initial 0, instead beginning the sequence with two 1s.In mathematical terms, the
sequence Fn of Fibonacci numbers is defined by the recurrence relation "

A lot of Fibonacci number appear in the phenomena of the natural world. For example, the number of petals is almost Fibonacci number or the number of sunflower seeds is Fibonacci number. They are very mysterious.