Why trees look like rivers and also blood vessels and also lightning…

Any time nature wants to minimize surface area for a volume it reaches for a sphere.

Any time nature wants to maximize surface area within a volume it reaches for a branching fractal.

Extremely efficient to define how to create one given its self-similar shape.

Lots of things in human and biological systems need to maximize their surface area for a given volume

Geoffrey West cataloged in Scale some of the implications of this space-filling shape.