"Embryo" might be a loaded word. At the stage at which stem-cells can be harvested, the fertilized egg is a "blastocyst," a tiny clump—a spheroid—of cells. If it isn't implanted in a woman's uterus, it will not develop any further, which is why it has to be frozen if it is to be preserved at all. These left-over blastocysts consist of undifferentiated cells—stem-cells. So at this point in its development it has no identity as much of anything, and definitely not as a unique individual.

If it is not placed in an environment where it can develop further (a woman's uterus), it will simply die. It can be preserved for a period of time by freezing, but that time is limited.

It will never be a human being.

So—ETHICALLY and MORALLY, which is better? To dispose of it as biological waste? Or to use it to cure or prevent diseases and save lives?

To me, the alternatives are clear-cut and obvious. I think it would be unethical and immoral to simply throw it away—kill it—when it's existence could be given some meaning by using it to cure diseases and save lives;   not just one life, but many.

I find it mind-boggling that some people can stare right at the obvious and still not see it.

Don Firth