Common alopecia (androgenic or androgenetic alopecia) cannot be cured in the sense that the lost follicles cannot be regenerated. However, the back and lateral areas of the head are genetically programmed to grow for life: these hair follicles are not affected by testosterone or alopecia. It is hair that does not fall out.
These areas where the hair does not fall out, which we call the 'donor area', allow us to select hair follicles that we can graft to the recipient area (where the hair has fallen out). Once grafted, they continue to grow normally and replace the lost hair.