During the development of a multicellular organism, cell differentiation involves activation and repression of transcription programs that must be stably maintained during subsequent cell divisions. Chromatin remodeling plays a crucial role in regulating chromatin states that conserve transcription programs and provide a mechanism for chromatin states to be maintained as cells proliferate, a process referred to as epigenetic inheritance inheritance of a gene activity state that is not specified by DNA sequence . A large number of factors and protein complexes are now known to be involved in regulating the dynamic states of chromatin structure. Their biological functions and molecular mechanisms are beginning to be revealed.