Baum, M. et al. Nat. Commun. 5, 4494 (2014).

To capture the dynamic structure of chromatin in living cells, Baum et al. used an approach established for diffusion nuclear magnetic resonance spectroscopy in which the mobility of a nanosensor is used to gather information about a structure. They traced the mobility of GPF monomers, trimers and pentamers in the cytoplasm and the nucleus by fluorescence correlation spectroscopy with a line-illuminating multifocus fluorescence microscope. The topology of the intracellular space determines accessibility and dwell time of proteins; the researchers' measurements allowed them to generate a model of the intracellular architecture at nanometer scale. Their findings point to random obstacle structures in the nucleus rather than fractal or corral structures with fixed sizes.