In humans, eight types of histone H1 exist (–, H1 , H1t and H1oo), all consisting of a highly conserved globular domain and less con-served N- and C-terminal tails. Although the precise functions of these iso-forms are not yet understood, and H1 subtypes have been found to be dispensable for mammalian development, it is now clear that specific func-tions may be assigned to certain individual H1 subtypes.