The Golden Section was known by Euclid in ancient Greece: ratio of  line's length to its larger portion where ratio of larger to smaller is same.  Approx 1.618 but an irrational number (ie cannot be described in a fraction).

Fibonacci described his epnymous number sequence (0, 1, 1, 2, 3, 5, 8 etc) in his original book of maths describing arab numerals – did NOT appear to see connection or its unique properties.

Seen when looking at geometry of dodeca/icosahedrons.

Can be expressed as 1+SQR 5/2

T
o reverse ratio, just subtract 1 (ie 0.618)

Solution to packing problem (only solved in 1900s). Produces spirals in both directions.

Square of one Fibonacci number is 1 plus or minus product of adjacent numbers!

Dali & LeCorbusier were fans of the Golden Section.