human embryonic stem cells are obtained from embryos, thereby they are subject to ethical, religious, political and legal considerations
Explanation:
Human embryonic stem cells (HESCs) are pluripotent undifferentiated cells derived from blastocyst-stage embryos, which have the ability to produce any type of somatic cells. HESCs are obtained <em>in vitro</em> from embryos that are 5-6 days old. These cells are valuable tools in research in order to understand the genetic and physiological mechanisms of human development, as well as to develop treatments against diseases. The use of embryonic stem cells in research is controversial because these techniques involve the destruction of human embryos, and there are people who consider human life begins with the formation of the diploid zygote after fertilization, thereby raising the debate if a human embryo can be regarded as a human being.
