Nuclear Structure and Gene Expression assimilates the contributions of genome organization and of the components of the nuclear matrix to the control of DNA and RNA synthesis. Nuclear domains which accommodate DNA replication and gene expression are considered in relation to short-term developmental and homeostatic requirements as well as to long-term commitments to phenotypic gene expression in differentiated cells. Consideration is given to the involvement of nuclear structure in gene localization as well as to the targeting and concentration of transcription factors. Aberrations in nuclear architecture associated with and potentially functionally related to pathologies are evaluated. Tumor cells are described from the perspective of the striking modifications in both the composition and organization of nuclear components. Nuclear Structure and Gene Expression presents concepts as well as experimental approaches, which define functionality of nuclear morphology.