Fractal dimension is a measure of how "complicated" a self-similar figure is.
In a rough sense, it measures "how many points" lie in a given set.
A plane is "larger" than a line, while S sits somewhere in between these two sets.
Fractal-like networks effectively endow life with an additional fourth spatial dimension.
This is the origin of quarter-power scaling that is so pervasive in biology.
The underlying principle of fractals is that a simple process that goes through infinitely many iterations becomes a very complex process.
Fractals attempt to model the complex process by searching for the simple process underneath.
Most fractals operate on the principle of a feedback loop.