Gradual Unpacking Eukaryotic DNA is packaged onto nucleosomes, which form the main constituent of chromatin. This packaging material presents a barrier to accessing the genome by the various machineries that need to deal with the DNA: replication, recombination, repair, and transcription complexes, for example. Hodges et al. (p. 626 ; see the Perspective by Otterstrom and van Oijen ) use single-molecule techniques to analyze how a yeast RNA polymerase II ternary elongation complex copes when it encounters a single nucleosome directly in its path. The polymerase does not actively peel the DNA from the nucleosome's surface but, instead, waits patiently until the DNA fluctuates off the nucleosome and then advances, increment by increment, until the nucleosome is destabilized. Under certain conditions the destabilized nucleosome, rather than being lost entirely from the DNA, can be passed back to the DNA behind the polymerase.