The golden rectangle

Leonardo Pisano was the first great mathematician of medieval
Christian Europe. He played an important role in reviving ancient mathematics and made great contributions of his own. After his death in 1240, Leonardo Pisano became known as Leonardo Fibonacci.
Leonardo Fibonacci was born in Pisa in about 1180, the son of a member of the government of the Republic of Pisa. When he was 12 years old, his father was made administer of Pisa's trading colony in Algeria. It was in Algeria that he was taught the art of calculating. His teacher, who remains completely unknown seemed to have imparted to him not only an excellently practical and well-rounded foundation in mathematics, but also a true scientific curiosity.
In 1202, two years after finally settling in Pisa, Fibonacci produced his most famous book, Liber abaci (the book of the Calculator). The book consisted of four parts, and was revised by him a quarter of a century later (in 1228). It was a thorough treatise on algebr...