Publisher Summary This chapter summarizes some of the evidence describing the three-dimensional (3-D) organization of interphase nuclei and correlates this evidence with results showing that the organization of interphase nuclei is dynamic and under the control of physiological stimuli. The considerable evidence indicates that specific chromatin domains in interphase nuclei of cells in vitro may move within the global confines of interphase nuclei. In addition, chromosome patterns in cells in vivo are dynamic, either during differentiation when cells exhibit stage-specific, characteristic patterns of centromeric satellite DNA or under conditions of altered functional states. Together, these results indicate that rearrangement of the spatial positions of specific chromatin domains may depend upon transcriptional demands of the cell and may be taken to indicate the presence of a potential link between the positioning of specific gene sequences and cell function. A body of evidence also indicates that rearrangement of chromosome patterns may occur in cells in vitro as well as in cells in vivo under pathological conditions. To ultimately assign a functional role to these phenomena, however, it would be necessary to show in intact cell assemblies that changes in the organization of chromatin domains within neuronal interphase nuclei may occur in response to physiological stimuli.