Is chromatin in the nucleus a liquid, a gel or a solid?
In plain words
Experiments disagree on whether chromatin flows like a thick liquid or holds its shape like a soft solid at scales below a micrometer. The answer decides how genes move and how mechanical forces reach the genome.
Precise statement
Determine the frequency-dependent storage and loss moduli $G'(\omega)$ and $G''(\omega)$ of interphase chromatin in living mammalian nuclei at length scales $10^{-5}\text{ to }10^{-4}\,\mathrm{cm}$ and times $10^{-2}\text{ to }10^{3}\,\mathrm{s}$, and reconcile reports of liquid-like condensed chromatin with solid-like behavior. Answer: the classification by scale, with the moduli.
What would settle it
Microrheology inside living nuclei with calibrated probes across the stated scales, cross-checked by response to applied force.
Status in the literature
A 2020 study (Strickfaden and co-workers) reported solid-like chromatin at the mesoscale, against liquid-like models; the dispute continues.