I was recently reminded of it when we were tending to a client's vegie garden where we had planted some, as it turned out, gorgeous sunflowers. Of course I didn't have my phone on me to take a pic. But today as i was wandering around The Home Depot that was just packed with very tempting colors of echinacea (coneflower), I was like
"aha! The Echinacea has a pretty obvious spiral!"
So that is the shot above.

So, what is the Fibonacci spiral aka the golden ratio?

(BORING math-y answer from some tech site)

"The Fibonacci sequence is a set of numbers that starts with a one or a zero, followed by a one, and proceeds based on the rule that each number (called a Fibonacci number) is equal to the sum of the preceding two numbers."

(@gardenlady's answer)

THE coolest spiral found in practically all plants like flower florets, pinecones, pineapples, ferns..not to mention ocean waves, sea shells, hurricanes, spiral galaxies, DNA molecules and more.

I'll just add this Tedtalk link here on Fibonnacci - it's actually cool to see how the numbers work - take a look if you have a few minutes