on human embryos led to more widespread controversy as criticism of the technique now began from the wider public who debated the moral ethics of questions concerning research involving human embryonic cells. Potential use in therapy Since pluripotent stem cells have the ability to differentiate into any type of cell, they are used in the development of medical treatments for a wide range of conditions. Treatments that have been proposed include treatment for physical trauma, degenerative conditions, and genetic diseases (in combination with gene therapy). Yet further treatments using stem cells could potentially be developed due to their ability to repair extensive tissue damage. Great levels of success and potential have been realized from research using adult stem cells. In early 2009, the FDA approved the first human clinical trials using embryonic stem cells. Only cells from an embryo at the morula stage or earlier are truly totipotent, meaning that they are able to form all cell types including placental cells. Adult stem cells are generally limited to differentiating into different cell types of their tissue of origin. However, some evidence suggests that adult stem cell plasticity may exist, increasing the number of cell types a given adult stem cell can become. Points of controversy Destruction of a human embryo is required in order to research new embryonic cell lines. Much of the debate surrounding human embryonic stem cells, therefore, concern ethical and legal quandaries around the destruction of an embryo. Ethical and legal questions such as "At what point does one consider life to begin?" and "Is it just to destroy a human embryo if it has the potential to cure countless numbers of patients and further our understanding of disease?" are central to the controversy. Political leaders debate how to regulate and fund research studies that involve the techniques used to remove the embryo cells. No clear consensus has emerged. Much of the criticism has been a result of religious beliefs and, in the most high-profile case, US President George W Bush signed an executive order banning the use of federal funding for any stem cell lines other than those already in existence, stating at the time, "My position on these issues is shaped by deeply held beliefs," and "I also believe human life is a sacred gift from our creator." This ban was in part revoked by his successor Barack Obama, who stated: "As a person of