The discovery of chromatin

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Chromatin is the genetic material of the nucleus consisting of deoxyribonucleoprotein that occurs in two forms during the phase between mitotic divisions: as heterochromatin (seen as condensed, readily stainable clumps) and as euchromatin (dispersed, lightly staining or nonstaining material). During mitotic division the chromatin condenses into chromosomes[1].


The German biologist Walther Flemming discovered[2] chromatin in 1879 while researching cell division. In his 1879 publication he notes the presence of thread-like substances distributed throughout the cell nucleus and which readily absorbs dyes such as aniline and haematoxylin. Here is an electron micrograph[3] of a rat’s liver cell nucleus (“N is the nucleolus) with its chromatin visible as dark granular clumps:


Here is a photograph[4] of Walther Flemming: