For those who don't know, this is the utilization of phi (~1.618), the golden ratio, in composition.
The result here is a "golden spiral", wherein each box, starting at the middle, has a side length ~1.618 times as long as the previous box's side length. A quarter circle is then drawn inside each box such that they connect to form a spiral. This type of logarithmic spiral is commonly found in nature, and, as such, artists use it as an aid in the composition of a piece.
