Barnsley Fractal

Have a look at Wikipedia. Extract below.

The Barnsley fern is a fractal named after the British mathematician Michael Barnsley who first described it in his book Fractals Everywhere. He made it to resemble the black spleenwort, Asplenium adiantum-nigrum.

The fern is one of the basic examples of self-similar sets, i.e. it is a mathematically generated pattern that can be reproducible at any magnification or reduction. Like the Sierpinski triangle, the Barnsley fern shows how graphically beautiful structures can be built from repetitive uses of mathematical formulas with computers. Barnsley's 1988 book Fractals Everywhere is based on the course which he taught for undergraduate and graduate students in the School of Mathematics, Georgia Institute of Technology, called Fractal Geometry. After publishing the book, a second course was developed, called Fractal Measure Theory. Barnsley's work has been a source of inspiration to graphic artists attempting to imitate nature with mathematical models.

Although this fractal is in the "Line Fractal" section of this website, and it seems to be built of lines, this is not true. The lines are created using an algorithm with randomness. This image is rendered using 300.000 iterations. You can play with the number of iterations by changing the value in the input box below.
With just 5000 iterations the fern shape is already recognisable.