Annotation: In my research, I investigate X-ray interactions with small isolated molecules, which trigger ultrafast nuclear dynamics occurring within just a few femtoseconds (10⁻¹⁵ s). Using high-resolution electron spectroscopy and electron-ion coincidence methods at synchrotron light sources, I explore phenomena such as ultrafast dissociation of short-lived intermediates, including the molecular catapult effect and nuclear dynamics during Auger cascade decays that lead to the complete disintegration of the molecule.