Only having seen one gecko in my life I’ve given them little thought. One thing I am sure of, however, is that I didn’t expect the answer to how geckos manage to navigate walls and ceilings so dextrously to be as awesome as it is.
The bottoms of a gecko’s feet are […] covered with millions of tiny foot-hairs on each toe, called setae, each about as long as the width of two human hairs (about 100 millionths of a meter). Each seta, in turn, is divided at the end into approximately a thousand tiny spatulae […] which are about 200 billlionths of a meter wide, which is smaller than the wavelength of visible light.
It seems the geckos’ toes create so much surface area in this way, with such tiny endings, that they are able to make use of Van der Waal’s force – a weak attractive force which is present between molecules – to stick themselves to the ceiling.