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.
To understand the pros and cons of stem cell research, one must first understand where stem cells come from. There are three main sources for obtaining stem cells-adult cells, cord cells, and embryonic cells. Adult stem cells can be extracted either from bone marrow or from the peripheral system. Bone marrow is a rich source of stem cells. However, some painful destruction of the bone marrow results from this procedure.