This is one of the first books that focuses on emerging concepts about the role of the structure of chromatin, the organization of the genome, and the structure of the interphase nucleus in the control of gene expression in eukaryotes. The first section analyses the relationship between thedynamic chromatin structure at the nucleosome level and gene expression. Section two looks into higher order chromatin structure in relation to transcription. In section three the molecular basis of epigenetic phenomena, like X-chromosome inactivation is discussed, starting from our understanding ofchromatin structure. Together, these topics form the molecular basis for our understanding of cell differentiation, knowledge that is essential for the design of transgenic animals and plants and for gene therapy in humans. The book is of direct interest to students that are new in the field and toinvestigators in the area of biomolecular sciences, like developmental biology, biochemistry, cell biology, microbiology and genetics. Also, those working in applied fields of research, i.e biotechnology and biomedicine, will strongly benefit from this book. It will help them to understandfundamental problems in transgenics and gene therapy. Importantly, a variety of human disorders may turn out to be caused by genetic or somatic errors related to this level of gene control.