A mathematical series of numbers first formulated by Indian scientists but popularised by Leonardo ‘Fibonacci’ of Pisa in 1202. Each number in the series is formed by adding up the previous two: 1, 2, 3, 5, 8, 13, 21…. Spiral leaf arrangements, the spiral packing of flowers in large heads, the spiral arrangement of cone scales, and the spirals of pineapple carpels all seem to follow the Fibonacci spiral, which gets wider every quarter turn by a changing factor related to the ratios of consecutive terms in the Fibonacci sequence.