Hence, some hours post-irradiation are requiredfor a full chromatin re-condensation even in apparently healthypatients. Besides, one will see below that dose repetition can pro-duce supra-additive effects with severe clinical consequences likelybecause a second dose applied when chromatin condensation hasnot recovered, renders more severe newly induced DNA damage(see below). The first techniques for assessing DNA breaks werealso used for estimating chromatin condensation/decondensation,as well