This article outlined biochemical methodologies for the labeling, detection, and analysis of newly replicated and newly assembled nucleosomes. The isolation of specific vertebrate factors that may be involved in chromatin assembly in vivo, such as nucleoplasmin, CAF-1, and NAP-1 and their counterparts in Drosophila and yeast add a further dimension to the study of nucleosome assembly in living cells. In particular, the ability to genetically manipulate the yeast system, together with the identification of yeast enzymes that acetylate newly synthesized H4, will certainly provide exciting new avenues for the investigation of chromatin assembly in vivo.