Stem cells are special human cells that have the ability to develop into many different cell types, ranging from muscle cells to brain cells, and can also fix damaged tissues. There are two main types of stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells are pluripotent, meaning they can turn into more than one type of cell, and are derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Adult stem cells, on the other hand, are found in fully developed tissues such as the brain, skin, and bone marrow, and are more likely to generate only certain types of cells.

Stem cells have unique abilities to self-renew and to recreate functional tissues. They can divide and renew themselves over a long time, are unspecialized, and have the potential to become specialized cells such as muscle cells, blood cells, and brain cells. Stem cells are different from other cells in the body in that they can renew themselves and develop into many different cell types.

Stem cells have the potential to be used in many different areas of health and medical research. Studying stem cells may help explain how serious conditions such as birth defects and cancer come about. Stem cells may one day be used to make cells and tissues for therapy of many diseases, such as Parkinsons disease, Alzheimers disease, spinal cord injury, heart disease, diabetes, and arthritis. However, there are still many hurdles that must be overcome before stem cells can be utilized for clinical use, and adverse effects such as tumors and unwanted immune responses have been reported.