Leonardo of Pisa or Leonardo Pisano (Pisa, c. 1170 - Pisa, 1250), also known as Fibonacci, was an Italian mathematician. He is best known for the discovery of the Fibonacci numbers, and for his role in the introduction to Europe of the modern Arabic positional decimal system for writing and manipulating numbers (algorithm).
It is believed that his nickname came from the latin "filius bonacci" which means "son of Bonacci". Fibonacci wrote the book "Liber Abaci" (Book of Abacus). He is also known for a major contribution called the Fibonacci series. Fibonacci series starts by 1,1,2,3,5... The numbers in the series follow this pattern: each one is the result of the sum of it's previous two numbers. The numbers in this series have the quality that if you divide each of them by the one before them, the result is an approximation to the golden ratio. The larger the two consecutive Fibonacci numbers are, the closer their ratio is to the irrational golden ratio.
It is believe that Fibonacci series explains in some way nature's growth path, taking into account the plenty of times the golden ratio is rediscovered in nature.
Bibliography: Hakim, J. "The story of science, Aristotle leads the way" Smithsonian Books, 2004, US