Size does matter: Viologen dications (blue) substituted with dendrons form strong host–guest complexes with molecular tweezers (yellow) in solution and in the gas phase (see picture). Complexation even stabilizes dications which are intrinsically unstable as “naked” species in the high vacuum of a mass spectrometer. A remarkably pronounced effect of dendrimer size on the stability of these dications switches their fragmentation between two mechanisms.