Nuclear functions are organized into distinct, non-overlapping subnuclear domains. Nuclear matrix, the underlying network of anastomising network of filaments and fibers provides structural basis for the functional compartmentalization of nuclear functions. Immunofluorescence microscopy of the nucleus in situ has revealed the distinct subnuclear distribution of vital nuclear processes, including (but not limited to) DNA replication sites, chromatin remodeling, e.g., mediated by the SWI/SNF complex and Runx factors, structural parameters of the nucleus, such as the nuclear envelope, chromosomes, and chromosomal territories, Runx domains for transcriptional control of tissue-specific genes; and RNA synthesis and processing involving, for example, transcription sites, SC35 domains, coiled bodies and nucleoli. Subnuclear PML bodies of unknown function have been examined in numerous cell types. All these domains are associated with the nuclear matrix.