For a long time, chromatin was only described as a mean to fit the two-meters long DNA molecule into a nucleus of only a few microns. It is admitted today that chromatin actually represents a key element in the regulation of all nuclear functions dependent on DNA. In the context of UV-induced DNA damage, chromatin undergoes a rapid and transient relaxation which leads to an expansion of the damaged area to 1.5 times its original size. While this chromatin response to damage is associated with a higher DNA accessibility, the link between those two phenomena, as well as the mechanisms driving them, are still poorly understood. Using live-cell imaging and laser micro-irradiation to induce DNA damage on specific nuclear areas, this work allowed to gain hindsight on the predominant role played by PARP1 in the DNA damage-induced chromatin relaxation. Indeed, showing that PARP1 at DNA damage sites can both induce chromatin compaction through its recruitment at DNA breaks or chromatin decondensation through its PARylation activity helped reconcile its apparent opposite effects described in the literature. A focus was also made on the linker histone H1, as it displays a peculiar behavior upon DNA damage, being rapidly released from the site of DNA lesions. Even if the driving force behind H1 release from damaged chromatin areas has not been identified yet, its behavior suggests that H1 might play a part in chromatin relaxation or in increasing DNA accessibility upon DNA damage. Lastly, combining photo-activation techniques and fluorescence correlation spectroscopy, experiments were performed in order to understand the physical environment that damaged, relaxed chromatin constitutes. We report here that, while enhanced binding of random DNA binding factors is observed in the damaged chromatin area, no significant change is observed in the macromolecular crowding levels that could potentially explain this enhanced binding, as well as a higher DNA accessibility.