Gecko foot hairs. Coloured scanning electron micrograph (SEM) of hairs, or setae, from a gecko's (family Gekkonidae) foot pad. These hairs enable the gecko to cling to smooth surfaces by taking advantage of weak intermolecular forces, known as Van der Waals forces. There are hundreds of thousands of setae on each foot. Magnification: x1800 when printed 10 centimetres wide.