Let's continue our explanation of epigenetics. As a reminder, our genetic information, in the form of DNA, is found in the nuclei of our cells. In each of these cells, two metres of DNA are compacted into small nuclei of about 10 micrometres. The different levels of compaction make some areas of our DNA accessible and others not. Thanks to these mechanisms, cells can select the genes they will express 'à la carte' according to their stage of development, external stimuli, energy needs, etc. How do our cells manage to do this - wrapping 2 metres of DNA into a nucleus 10 times smaller than the diameter of a hair? This is the question we were left with. Part of the answer can be found in the illustration below. Protein complexes, called nucleosomes (in light blue), form a structure around which the DNA strands (in pink) are wound. A bit like a boat's rope around a mooring bitt in a harbour. The composition of these nucleosomes can vary according to the different needs of the cell.