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Digital image correlation is a measurement technique that allows one to retrieve displacement fields' separating'two digital images of the same sample at different stages of loading. Because of its remarkable sensitivity, it is possible to not only detect cracks with sub-pixel opening, which would not be visible but also to provide accurate estimates of stress intensity factors. For this purpose suitable tools have been devised to minimize the sensitivity to noise. Working with digital images allows the experimentalist to deal with a wide range of scales from the atomistic to the geophysical one with the same tools. Various examples are shown at different scales, as well as some recent extensions to three-dimensional cracks based on x-ray Computed micro-tomographic images.