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.
1 Fetal stem cells-These cells are taken from the germline tissues that will make up the gonads of aborted fetuses. 2  Umbilical cord stem cells-Umbilical cord blood contains stem cells similar to those found in bone marrow. Umbilical cord stem cells-Umbilical cord blood contains stem cells similar to those found in bone marrow. 2  Placenta derived stem cells-Up to ten times as many stem cells can be harvested from a placenta as from cord blood. 3  Adult stem cells-Many adult tissues contain stem cells that can be isolated.