Fractals are not only mathematical abstraction, which can be used for creation of abstract or realistic images (see
images by Keith Mackay). They can be found in our world in various plants, shells etc. Below you can see several examples of fractals in nature.
The most known fractal is fern leaf. Every little leaf of fern repeats whole large leaf.
Another interesting nature fractal is
romanesco cauliflower, which is a cross between broccoli and Cauliflower, which accentuates the great fractal spiral patterns on the top.

In cactus below leafs become twisted towards the center.

Fractals also exists in
micro world. Viruses, mould and bacterial aggregate colonies spontaneously assume fractal shapes.

The best known fractal representation among animals is nautilus shell.
Lightning Strikes and Electrical Discharge creates fractal formations called
Lichtenberg figures on rocks, grass,wood or even people!

Many symmetrical wonderful fractal shapes can be found in snowflakes.
This post was created by
materials of
http://www.its.caltech.edu/~atomic/snowcrystals/http://www.miqel.com/fractals_math_patterns/visual-math-natural-fractals.html