To fit inside cells, DNA is wrapped around protein spindles called nucleosomes.The nucleosomes themselves are then coiled into structures called chromatin.
When the DNA needs to be read, the nucleosome stacks that compose chromatin fall apart and reform again within milliseconds. This dance allows DNA-reading machinery within the cell access to the DNA.
The intricate details of this dance – illustrated above – have only recently been observed by Swiss researchers, using fluorescence spectroscopy.