Question: Stem cells can be found in which organisms?
About the article "Stem cell", section "Abstract".

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Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues.
Also known as somatic stem cells (from Greek Σωματικóς, meaning "of the body"), they can be found in juvenile as well as adult animals and human bodies.
Scientific interest in adult stem cells is centered on their ability to divide or "self-renew" indefinitely, and generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells.
Unlike embryonic stem cells, the use of human adult stem cells in research and therapy is not considered to be controversial, as they are derived from adult tissue samples rather than human 5 day old embryos generated by IVF (in vitro fertility) clinics designated for scientific research.
They have mainly been studied in humans and model organisms such as mice and rat. 
Stem cells are cells found in all multi-cellular organisms.
They were isolated in mice in 1981, and in humans in 1998.
In humans there are many types of stem cells, each with varying levels of potency.
Potency is a measure of a cells differentiation potential, or the number of other cell types that can be made from that stem cell.
Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst.
These stem cells can differentiate into all other cells in the human body and are the subject of much scientific research.
However, since they must be derived from early human embryos their production and use in research has been a hotly debated topic as the embryo most likely is destroyed in the process.
Stem cell treatments are a type of cell therapy that introduce new cells into adult bodies for possible treatment of cancer, diabetes, neurological disorders and other medical conditions.
Stem cells have been used to repair tissue damaged by disease or age.
Cloning also might be done with stem cells.
Pluripotent stem cells can also be derived from Somatic cell nuclear transfer which is a laboratory technique where a clone embryo is created from a donor nucleus.
Somatic cell nuclear transfer is also tightly regulated amongst various countries.
Until recently, the principal source of human embryonic stem cells has been donated embryos from fertility clinics.
In January 2007, researchers at Wake Forest University reported that "stem cells drawn from amniotic fluid donated by pregnant women hold much of the same promise as embryonic stem cells.
"In 2000, the NIH, under the administration of President Bill Clinton, issued "guidelines that allow federal funding of embryonic stem-cell research."
Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells.
They are found in multicellular organisms.
In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues.
In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues.
In a developing embryo, stem cells can differentiate into all the specialized cells—ectoderm, endoderm and mesoderm (see induced pluripotent stem cells)—but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.
There are three accessible sources of autologous adult stem cells in humans:
 Bone marrow, which requires extraction by "harvesting", that is, drilling into bone (typically the femur or iliac crest),
 Adipose tissue (lipid cells), which requires extraction by liposuction, and
 Blood, which requires extraction through apheresis, wherein blood is drawn from the donor (similar to a blood donation), and passed through a machine that extracts the stem cells and returns other portions of the blood to the donor.
Stem cells can also be taken from umbilical cord blood just after birth.
Of all stem cell types, autologous harvesting involves the least risk.
By definition, autologous cells are obtained from one's own body, just as one may bank his or her own blood for elective surgical procedures.
Adult stem cells are frequently used in medical therapies, for example in bone marrow transplantation.
Stem cells can now be artificially grown and transformed (differentiated) into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves.
Embryonic cell lines and autologous embryonic stem cells generated through therapeutic cloning have also been proposed as promising candidates for future therapies.
Research into stem cells grew out of findings by Ernest A. McCulloch and James E. Till at the University of Toronto in the 1960s.
  Gamete - A haploid reproductive cell.
Sperm and ova are gametes.
Gametes fuse with another gamete during fertilization (conception) in organisms that reproduce sexually.
* Sperm - Male reproductive cell (a gamete).
* Ovum - Female reproductive cell (a gamete).
Zygote - A cell that is the result of fertilization (the fusing of two gametes).
* Egg - The zygote of most birds and reptiles, resulting from fertilization of the ovum.
The largest existing single cells currently known are (fertilized) eggs.
Meristemic cell - Undifferentiated plants cells analogous to animal stem cells.
Stem cell- Undifferentiated cells found in most multi-cellular organisms which are capable of retaining the ability to reinvigorate themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types.
Germ cell - Gametes and gonocytes, these are often .
Germ cells should not be confused with "germs" (pathogens).
Somatic cell - any cells forming the body of an organism, as opposed to germline cells.  
Most progenitors are described as oligopotent.
In this point of view, they may be compared to adult stem cells.
But progenitors are said to be in a further stage of cell differentiation.
They are in the “center” between stem cells and fully differentiated cells.
The kind of potency they have depends on the type of their "parent" stem cell and also on their niche.
Some progenitor cells were found during research, and were isolated.
After their marker was found, it was proven that these progenitor could move through the body and migrate towards the tissue where they are needed.
Many properties are shared by adult stem cells and progenitor cells.
But still, controversy remains because embryonic stem cells are true stem cells in that they are pluripotent and show unlimited capacity for self-renewal.
In contrast, many cells termed adult stem cells would be better defined as progenitor cells, as their capacities for unlimited self-renewal and plasticity have not been comprehensively demonstrated.
Progenitor cells are found in adult organisms and they act as a repair system for the body.
They replenish special cells, but also maintain the blood, skin and intestinal tissues.
They can also be found in developing embryonic pancreatic tissue.