['In comparison with many nuclear proteins, the movement of chromatin in nuclei appears to be generally constrained. These restrictions on motion are proposed to reflect the attachment of chromatin to immobile nuclear substructures.', 'To gain insight into the regulation of chromosome dynamics by nuclear architecture, we have followed the movements of different sites in the human genome in living cells. Here, we show that loci at nucleoli or the nuclear periphery are significantly less mobile than other, more nucleoplasmic loci. Disruption of nucleoli increases the mobility of nucleolar-associated loci.'] Is chromatin motion constrained by association with nuclear compartments in human cells?