Fibonacci numbers are a sequence of numbers where each number is the sum of the two preceding ones. The sequence starts with 0 and 1, so it goes: 0, 1, 1, 2, 3, 5, 8, 13, and so on. This pattern was introduced to the Western world by the mathematician Leonardo of Pisa, also known as Fibonacci, in his book published in 1202. These numbers appear in various aspects of nature, such as the arrangement of leaves on a stem or the pattern of seeds in a sunflower. The Fibonacci sequence is also used in art and architecture, often associated with the Golden Ratio, which is believed to create aesthetically pleasing proportions.