“…Techniques such as fluorescence recovery after photobleaching (FRAP) or green florescence protein (GFP) recovery have demonstrated that over time, even condensates that start displaying liquid-like behaviour can 'age' or 'mature' (i.e., change their material properties), transitioning into gels or soft glasses [20,21,25]. Notably, particle tracking microrheology techniques have been also successfully employed to evaluate the mean squared displacement (MSD) of marked beads inside droplets, and then, via that MSD and the Stokes-Einstein relation, the viscosity of the condensates can be inferred [25,[53][54][55][56]. Moreover, the progressive dynamical arrest of proteins has been also observed in vitro for protein condensates containing marked prion-like domains (PLDs) enriched in LARKS [3,19,21,22,33,35,36,44,[57][58][59][60].…”