Widmanstätten figures are found in octahedrite meteorites. To see these figures, the inside surface of the meteorite must first be polished. It is then etched with acid. Because kamacite and taenite react differently to acid, a mesh-like structure appears. These figures form only at the centre of planetary bodies that took millions of years to cool. They do not exist on Earth. The width of the kamacite bands are used to calculate the cooling rate of the parent asteroid, which can in turn be used to deduce its size.