Researchers have studied stem cells and their effects on the body and have come to the conclusion that there is more than one type in the human body. They are recognized as the following:

Totipotent	Contains the full potential to become another embryo. These cells are only found a few days after fertilzation. If one of these cells are seperated from the others, it has the capability to become another human being with the same genetic makeup as the other.
Pluripotent	These are the totipotent cells which have already started undergoing differentiation. These cells retain the possibility of becoming body cells but no longer has the ability to produce another human on it's own.
Multipotent	These cells are even further specialized to become only a limited number of body cells.

The existence of stem cells were known in the past, but it was not until researchers successfully grew human embryonic cells in a lab in 1998, that interest was piqued. Attempts are now being made to grow large numbers of stem cells in hopes that they can be manipulated to become specific cell types. If this is successful, it would become a great medical advantage to people everywhere. For example, the possibility of cultivating organs for transplants would prove to be a great benefit to patients in need of it. The problem concerning rejection of the organ from the patient's immune system would no longer be an issue. The organ would be the exact same genetic makeup as the person.