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Ferrite etches faster in Nital, so it recedes and leaves cementite standing as the higher ridges. The identification is based on the surface-relief preparation, not on assuming that every bright feature in every microscopy mode is cementite. In the stated AFM image, brightness is a displayed height contrast.

The lamellae are ferrite and cementite, together forming pearlite. The displayed quantity is surface height in an atomic force microscopy image. Nital preferentially attacks the ferrite, leaving it lower and therefore darker; the narrow raised cementite lamellae appear bright. This is not the same contrast mechanism as brightness in an optical micrograph. Faster cooling that still permits pearlite formation causes transformation at greater undercooling and generally gives finer lamellar spacing. Cooling sufficiently rapidly to bypass diffusional transformation instead produces other products, potentially martensite; it does not merely keep making pearlite indefinitely finer.