After millions of years of evolution, nature has developed materials and systems based on the concept of damage management (healing) to extend survival possibilities. In the last 20. years, the dream of implementing this concept to engineering systems to extend service lifetime has become a reality. The field of self-healing engineering materials is growing exponentially, both in the number of research groups involved as well as the number of concepts explored, although finding applications for many of these new concepts is not straightforward. In this chapter, we focus on analyzing the main mechanisms and concepts developed in the field of self-healing polymers and introduce some explored applications of healable polymers, all from the point of view of understanding the concept of healing as the restoration of lost functionalities.@en