The leaves of Lotus plants have the unique ability to avoid getting dirty. They are coated with wax crystals around 1 nanometres in diameter that repel water. Droplets falling onto the leaves bead-up and if the surface slopes slightly will roll off taking dirt with them, so that the leaves are self-cleaning.

At the nanoscale rough surfaces are effective in repelling water than smooth ones as there is less contact between water and solid. This rough surface structure is also essential to the easy-cleaning effect on a smooth surface such as glass.