Since the advent of FISH (fluorescence in situ hybridization), there have been 
major advances in our understanding of how the genome is organized in interphase 
nuclei. Indeed, this organization is found to be non-random and individual 
chromosomes occupy discrete regions known as territories. Determining the 
factors that drive the spatial positioning of these territories within nuclei 
has caused much debate; however, in proliferating cells, there is evidently a 
correlation between radial positioning and gene density. Indeed, gene-poor 
chromosomes tend to be located towards the nuclear edge, while those that are 
more gene-rich are positioned more internally. These observations pose a number 
of questions: first, what is the function of this global organization and, 
secondly, is it representative of that occurring at a more local scale? During 
the course of this review, these questions will be considered, in light of the 
current literature regarding the role of transcription factories and the nuclear 
matrix in interphase genome organization.