Ordered crack patterns are so common in nature that they are often overlooked. From tile-like formations in ordinary mud, to the vast polygonal networks that stretch across the polar deserts of Earth and Mars, they are typical features in geomorphology. On smaller scales, crack networks add an artistic flourish to Japanese raku pottery and are found on the paintings of the old masters. Cracking even determines the pattern of scales on the snouts of Nile crocodiles.