The body is capable of healing itself. In fact, each cell can renew itself regularly. This is the most distinctive characteristic of stem cells which is found in most multi-cellular organisms. Through culture, these can now be transformed to specialized cells that are consistent with other tissues like muscles or nerves.

Among human beings, stem cells are categorized into two types: the embryonic and adult stem cells. Embryonic stem cells come from inner cell mass of blastocyst. This occurs 4-5 days after fertilization. Adult stem cells on the otherhand are undifferentiated and can be found only on adult tissues. They have this amazing capability to renew themselves indefinitely.