[en] Biophysical analyses of radiation tracks emphasize the importance of very local clustering of atomic damage within a track over microscopic distances as small as a few nanometres. They show that there must be a wide spectrum of initial physical damage within or very near to relevant macromolecules, such as DNA, and that the chemical, biochemical, repair and cellular consequences should differ considerably across this spectrum. An attempt has been made to divide this spectrum into four broad classes in order to guide development and application of assays which may better reveal the complexities and relevance of damage to DNA, and associated structures, within these classes. (author)