Our results may delineate a coherent picture of the behavior of the triplet state of thymine embedded in B-DNA and of the role of the environment. While ⇡ stacking appear fundamental in stabilizing the triplet state, and hence in opening the way to photosensitization, the spin density appears localized, and spin polarization, rather than excitonic delocalization, should be responsible for the altered photophysical properties. Of note, we should also underline that the reduced role of delocalization, as evidenced in our work, could also results from the fact that using MD simulations we may account for thermal disorder e↵ects. On the contrary, idealized and ordered model systems, having a perfect symmetry, are, obviously, nonphysically over emphasizing delocalization.