The answer would be the cell wall or the cell membrane
<span>Stem cells are found in multicellular organism,they are undifferentiated in nature and can form other special cells or could divide in further stem cells by mitosis.The person with brain or spinal cord injury would be interested cause these cells could be used in future to cure the problem.Human embryonic stem cell (HESC) research is ethically and politically controversial because it involves the destruction of human embryos.The resource used was paper by B Lo named 'Ethical Issues in Stem Cell Research'.And according to me research in this field is important for development of mankind</span>
One example is using tree rings on a tree to determine the absolute time
