An element is a pure substance that is made from a single type of atom. Elements are the building blocks for all the rest of the matter in the world. Examples of elements include iron, oxygen, hydrogen, gold, and helium.
Since the initial discovery that the adult brain contains stem cells that generate new neurons, an important question in neurobiology has been whether or not this adult neurogenesis is functionally important.
Stem cell. Stem cells are cells which are not terminally differentiated and are therefore able to produce cells of other types. Medical researchers hope they can be used to grow specific tissues or organs.There are three types of stem cells: totipotent, pluripotent, and multipotent.A single totipotent stem cell can grow into an entire organism.nother controversy in the use of embryonic stem cells is the use of therapeutic cloning. This involves the cloning of early embryos from which stem cells are harvested, providing a larger source of the cells. Many see this as encouraging human cloning, which they think could be dangerous or unethical.