Haven't heard about the golden ratio before? 

The golden ratio can also be called golden mean or golden section.

Sometimes it also goes by other names such as: extreme and mean ratio, medial section, divine section, golden proportion, golden cut and golden number.  

Some twentieth-century artists and architects, including Le Corbusier and Dalí, have proportioned their works to approximate the golden ratio—especially in the form of the golden rectangle, in which the ratio of the longer side to the shorter is the golden ratio—believing this proportion to be aesthetically pleasing. 

The golden ratio appears in some patterns in nature, including the spiral arrangement of leaves and other plant parts.

Mathematicians have studied the properties of the golden ratio for decades, including its appearance in the dimensions of a regular pentagon and in a golden rectangle, which may be cut into a square and a smaller rectangle with the same aspect ratio. 

The golden ratio has also been used to analyze the proportions of natural objects as well as man-made systems such as financial markets, in some cases based on dubious fits to data.

Check out some images below: 

For an in-depth explanation check out this article from Live Science.