Recent advances in polymer and materials chemistry have led to the development of materials that exhibit the ability to undergo repair. Depending on the structure and chemical composition of the material, the repair process can occur either as a result of external stimuli or autonomously and can be a one-time event or an indefinitely repeatable process. Several systems have been demonstrated recently in the literature; however, a larger number of polymeric systems have the potential to exhibit similar mending capability. These polymeric systems all share one property in common—reversibility, either in the polymerization process or in the cross-linking process. This Feature Article will outline the various known systems that encompass the ability to mend, either by external stimuli or autonomously. In addition, several non-reversible composite systems will be presented that exhibit one-time autonomous healing.