Few recent advances in science have generated as much excitement and controversy as human embryonic stem cells. The potential of these cells to replace diseased or damaged cells in virtually every tissue of the body heralds the advent of an extraordinary new field of medicine. Controversy arises, however, because current techniques required to harvest stem cells involve the destruction of the human blastocyst. This even-handed, lucidly written volume is an essential tool for understanding the complex issues--scientific, religious, ethical, and political--that currently fuel public debate...