Folding is fairly nifty.
For one thing, it lets you increase surface area without increasing volume. Which is why radiators are folded into sections or have multiple fins, allowing heat to escape maximally into the surrounding air via convection off the expanded surfaces and why ostriches fold their wings and legs against their bodies at night to cut down on heat loss. Our lungs pack a lot of oxygen transferring surface — 2,400 kilometres of airways! — into a comparatively modest volume thanks to a kind of folding. And our “little grey cells” find themselves on folds surrounding unfolded . . . [more]