Fibonacci was an Italian mathematician born in 1170 who introduced the Hindu-Arabic numeral system to Europe. He is most known for the Fibonacci sequence, where each number is the sum of the previous two, starting with 0 and 1. These numbers appear often in nature, such as the spiral of a nautilus shell or the petals of flowers. The ratios of numbers in the Fibonacci sequence approach the golden ratio, about 1.6, which has been considered aesthetically pleasing, appearing in architecture, art, and the human body.