Rheological characterization of polymeric systems can be used to investigate molecular processes. Some processes, such as entanglement and reptation, cannot be easily seen in the complex modulus or other conventional representations of rheological data. Instead, presenting data as relaxation spectra enhances the understanding of such processes. This will be shown on the example of ring and linear polystyrene polymers and ring/linear-blends, recently published by Kapnistos et al. (Nature Materials, 2008).