English: The dark circles are micro-pillars formed by an electrohydrodynamic instability in a thin polymer film. The pillars were created by spin-coating a liquid polymer onto an electrode to be used in a parallel plate capacitor. A top electrode is then placed on top of the first with an air gap between them. When a voltage is applied across the two capacitor electrodes, the pillars grow in the liquid polymer as a result of electrohydrodynamic instabilities at the interface between the polymer and the air. The brightly coloured areas (left) show where pillars are forming. The pillars are 20x smaller than the width of a human hair. The colours in the image are the result of thin film interference where light interacts with very thin layers of material. The resulting surfaces are used in tissue culture and optics.