This short video explains that stem cells are special cells that can develop into different types of cells, and are found in all organisms, including plants, animals, and humans.
Human stem cells can come from infant stem cells or adult stem cells. Embryonic stem cells come from blastocysts, which are formed about 5-6 days after fertilization and have an inner cell mass that forms the embryo and an outer cell mass that forms the placenta.
However, embryonic stem cell research is controversial due to ethical and political concerns.
Adult stem cells are found in tissues such as skin, intestine lining, and bone marrow, and have varying differentiation potentials. Multi-potent stem cells, such as hematopoietic and mesenchymal stem cells, can differentiate into specific types of cells.
Neural stem cells can self-renew and give rise to various types of cells in the central nervous system.