Fibonacci, also known as Leonardo of Pisa, was an Italian mathematician from the Middle Ages. As a boy, he travelled to North Africa with his merchant father, where he learned the Hindu-Arabic numeral system (the 0-9 digits we still use today). In 1202, he wrote a book called Liber Abaci, which introduced this system to Europe and helped replace the older, clumsier Roman numerals. He is best remembered today for the Fibonacci sequence, a pattern of numbers he used as an example in his book.
