The golden ratio is a special irrational number which is approximately
equal to 1.618, denoted by the Greek letter 'phi'. Aesthetic art forms such as the Great Pyramid of Giza,
the Mona Lisa, the Parthenon of Athens feature this ratio. It appears in famous logos of Apple, Pepsi and
Twitter. 'Rule of thirds' in photography stems from this ratio of beauty. This divine ratio occurs in nature
- the human body, in plants, the DNA of organisms and so on. For example, the length of our face divided by
its breadth gives us the golden ratio. Mathematically, phi^2 = phi +1.