Spin coating is a procedure used to apply uniform thin films to flat substrates. In short, an excess amount of a solution is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force. Rotation is continued while the fluid spins off the edges of the substrate, until the desired film thickness is achieved. The applied solvent is usually volatile, and simultaneously evaporates. Hence, the higher the angular speed of spinning, the thinner the film. The thickness of the film also depends on the concentration of the solution and the solvent, and can range from <10 nm to several micrometers. Despite the considerable material loss involved, the convenient combination of simplicity and reproducibility makes this technique a popular deposition tool in lab-scale production of the active layers of organic electronics and biosensors. It is also intensively used in photolithography to deposit photoresist.