The tokay gecko uses nanotechnology to stick itself to trees, walls, windows, and even ceilings. The gecko's feet are covered in microscopic hairs, called setae, which branch into thousands of smaller hairs with paddle-shaped ends. Those branches, or spatulae, are a mere 200 nanometers wide at the tip.
The extra surface area of the spatulae maximizes the effect of van der Waals forces, the weak electrical pull between every molecule in the gecko and every molecule in whatever it's sticking to. The combined force is so strong that a gecko can hang its whole weight from a single toe, even on a sheer piece of glass. Engineers have used carbon nanotubes mimicking gecko setae to create super-sticky tapes, glues, and even a wall-climbing gecko robot.