Why not use adult stem cells for research and stay away from the whole embryonic stem cell issue?
Although there are many ethical and scientific issues with embryonic stem cells, these cells have the greatest capacity to make new tissues. To date, adult stem cells have not been shown to give rise to the variety of tissues that embryonic stem cells potentially can. Additionally, under certain conditions, embryonic stem cells can form cancerous cells. For this reason, embryonic stem cells have the potential to be studied as a model of cancer development.