This image displays how the florets in the head of a sunflower form a beautiful spiral pattern. Even more interestingly, there are exactly 21 spirals in one direction, and 34 spirals in the opposite direction - and these are Fibonacci numbers, intrinsically related to the golden ratio. These patterns are seen in plants of all kinds from all over the world, such as in pineapples with 8/13 spirals, or cauliflower florets with 5/8 spirals - also Fibonacci numbers. This short video series discusses how such patterns arise, concluding that plants aren't actively planning such intricate designs - they are the result of a much more elegant underlying mechanism related to resource partitioning and growth that can explain a multitude of beautiful patterns in nature.
--Cory Weller