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 cells are categorized by their potential to differentiate into other types of cells. Embryonic stem cells are the most potent since they must become every type of cell in the body. The full classification includes: 1  Totipotent-the ability to differentiate into all possible cell types.2  Examples are the zygote formed at egg fertilization and the first few cells that result from the division of the zygote.tem cells are a class of undifferentiated cells that are able to differentiate into specialized cell types. Commonly, stem cells come from two main sources: 1  Embryos formed during the blastocyst phase of embryological development (embryonic stem cells) and. 2  Adult tissue (adult stem cells).