Many kinds of geckos can walk on trees, walls, windows, and ceilings. Geckos' feet form a molecular bond with the surface that they are walking on in order to "stick" to the surface. This force is called van der Waal's force.They can do this because they have special toe pads. A microscope can show that each toe pad is made of thousands of hair-like structures called setae. Each of these structures branches into many smaller ends called spatulae. The rest of their skin is also covered in extremely small hairs, which make it hard for a gecko to get wet. Gecko skin can also kill bacteria.