The present invention relates to novel activatable particles which can be used in the health sector. The invention more particularly relates to composite particles which can generate free radicals or heat when excited by X rays, and to the uses thereof in health, particularly human. The inventive particles comprise an inorganic-based, and optionally organic-based, nucleus and can be activated in vivo, in order to label or alter cells, tissues or organs. The invention also relates to methods for the production of said particles, and to pharmaceutical or diagnostic compositions containing same.
