Some cells can replicate like skin, muscle and blood cells.  When a cell divides to make a new cell, it is called replicating.  Some cells can't replicate as well, like brain, nerve, some muscle and badly damaged  kidney and liver cells.  Scientists are working  on ways to make cells reproduce or repair to help with diseases.  This would be great for Alzheimer disease, spinal cord injuries, or other nerve injuries, multiple sclerosis, muscular dystrophy, liver diseases and kidney failure.  This list of problems could go on and on.

 

	A stem cell is a very special cell that can get orders to change into different kinds of cells.  They can change into many kinds of cells such as muscle, blood (bone marrow), nervous tissue, bone,  cartilage and skin cells.  Scientists are pretty sure that stem cells are everywhere in your body, but they are not sure of what they look like.  Scientists are still learning how to control the growth of stem cells.
	This diagram shows that some stem cells can change into different cells.  Stem cells are given commands to change.  In the process, stem cells get more mature and decide what kind of cells they will be.  A "committed stem cell"  means that they probably cannot change into a different type of stem cell. When a cell has fully changed into a mature cell type, such as a nerve cell, it cannot change back into a stem cell and it cannot change into any other kind of cell like a muscle cell.
	These are nerve cells.  They used to be stem cells.  The stem cells were treated with retinoic acid, which is Vitamin A.
	Can you imagine how good it would be to make new nerve cells grow....  to fix the nerves in the spine.... so that  this person would not have to be in a wheelchair!