An example of a Fibonacci sequence of numbers in the segmentation of a pinecone. Looking at the image from the bottom, thirteen spirals go one way (clockwise) and eight the other. The yellow stickers show one of the eight anticlockwise spirals before it meets the first one again. Eight and thirteen are Fibonacci numbers, in which each member of the series is the sum of the previous two (e. g. 0, 1,1,2,3,5,8,13,21 etc. ). Five and twenty-one (also Fibonacci numbers) spirals are also visible.