The Golden Section
The Golden Section is based on a ratio which results in
phi
Take a line and divide it so that the ratio of the large piece (B) to the whole line (A) is the same as the ratio as the small
piece (C) to the large piece (B):
So A is 161.8% of B and B is 161.8% of C.
This ratio has been used by mankind for centuries
Its use started as early as with the Egyptians in the design of the
pyramids,
The Greeks knew
it as the
Golden Section 
The Renaissance artists
knew it as the
Divine Proportion 


and used it for beauty
and balance in the
design of architecture 
and used it for beauty
and balance in the
design of art 
It was used in the design of Notre Dame in Paris
and continues today in many examples of art, architecture and design. 