The Paris Metro is a branched network with a fractal form.

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When shaken vertically, a shallow layer of grains can develop complex wave patterns, including stripes, square and hexagonal patterns.

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The adult zebra Equus grevyi (b) has more and narrower stripes than the adult Equs burchelli (a). This is thought to be because the striped 'pre-pattern' is laid down on the embryo of the latter at an earlier stage: after twenty-one days for Equus burchelli (c), but after five weeks for Equus grevyi (e). The smaller embryo supports fewer stripes, and so by the time it is of comparable size (d), its stripes are wider.