The recent two years have led to the realization that histone chaperones contribute to the delicate balance between nucleosome assembly and re-assembly during transcription, and may in fact be involved as much in histone eviction as they are in chromatin assembly. Recent structural studies (in particular, the structure of an Asf1-H3/H4 complex) have suggested mechanisms by which this may be accomplished. The incorporation of various histone variants into nucleosomes has diverse effects on nucleosome structure, stability, and the ability of nucleosomal arrays to condense into chromatin higher order structures. It is likely that these seemingly independent ways to modify chromatin structure are interdependent.