This is a dried-up leaf of a Drynaria plant.
All that is left of it is the intricate network of veins that demonstrates anastomosis, which transports nutrients and water.
This network behavior can be found in the blood vessels of the retina, in river systems, and even in the roots of vines growing on the trunk of the trees (picture 3).
This has proved to be optimal in delivering fluctuating loads of product (water, blood) even when a vein is damaged; something that scientists and engineers take interest in, especially in studying cutting costs and hindering supply losses in electricity lines and water pipe networks.
Yet another feat we can learn from Nature.