They can be classified as to the origin in embryonic stem cells and adult stem cells and about the potential for totipotent, pluripotent or multipotent.

There are many therapeutic applications for these cells and there are several studies about this potential therapeutic use in the future with positive results and other that need further investigation in the future. These cells also can be used with the new therapeutic systems and varied subjects, such as cancer therapy, cardiovascular therapy and the neural therapy will be operated as well as some future scientific applications in these areas.

Stem cells can be classified according to their origin in cells embryonic stem cells or adult stem cells. Embryonic stem cells are isolated directly from the embryo at the initial stage of development (between the 4th and 6th day of embryonic development) and have a large ability to differentiate; adult stem cells are cells that are present in organs and fetal and adult tissues, having various origins from cord blood umbilical, placenta, adipose tissue, bone marrow, peripheral blood and mature tissues.

Umbilical cord blood represents one of the main sources of embryonic stem cells because the adult stem cells that reside there are in smaller numbers, therefore, it becomes a very promising source of cells in the area of regenerative medicine, in hematopoietic transplants and for the treatment of various hemato-oncological diseases.

Stem cell therapy, also known as regenerative medicine, promotes the repair response of diseased, dysfunctional or injured tissue using stem cells or their derivatives. It is the next chapter in organ transplantation and uses cells instead of donor organs, which are limited in supply. These stem cells are manipulated to specialize into specific types of cells, such as heart muscle cells, blood cells or nerve cells.

The specialized cells can then be implanted into a person. For example, if the person has heart disease, the cells could be injected into the heart muscle. The healthy transplanted heart muscle cells could then contribute to repairing defective heart muscle.

Researchers have already shown that adult bone marrow cells guided to become heart-like cells can repair heart tissue in people, and more research is ongoing.

In stem cell transplants, stem cells replace cells damaged by chemotherapy or disease or serve as a way for the donor's immune system to fight some types of cancer and blood-related diseases, such as leukemia, lymphoma, neuroblastoma and multiple myeloma. These transplants use adult stem cells or umbilical cord blood. Researchers are testing adult stem cells to treat other conditions, including a number of degenerative diseases such as heart failure.

For embryonic stem cells to be useful in people, researchers must be certain that the stem cells will differentiate into the specific cell types desired.

Researchers have discovered ways to direct stem cells to become specific types of cells, such as directing embryonic stem cells to become heart cells. Research is ongoing in this area.

Embryonic stem cells can also grow irregularly or specialize in different cell types spontaneously. Researchers are studying how to control the growth and differentiation of embryonic stem cells.

Embryonic stem cells might also trigger an immune response in which the recipient's body attacks the stem cells as foreign invaders, or the stem cells might simply fail to function normally, with unknown consequences. Researchers continue to study how to avoid these possible complications.