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.
Discovered in the 1960s, blood stem cells (haematopoietic stem cells) were the first stem cells to ever be discovered. Blood stem cells primarily reside in bone marrow and make all the cells found in blood, including cells important for the immune system. Transplants of blood stem cells have become widely used to treat diseases such as leukaemia, anaemia and autoimmune diseases.