Chromatic and spherical aberration-corrected atomic-resolution transmission electron microscopy combined with density-functional theory calculations is employed to elucidate the stability and dynamics of admolecules on suspended graphene. The results presented provide evidence that the interaction between the molecules and hydrogen adatoms leads to a mutual trapping. These ``symbiotic'' configurations can explain the presence of stable admolecules on graphene at ambient temperature. It is proposed to exploit these configurations to functionalize and dope graphene.