Thomson, et al. v. Thompson, et al. was a lawsuit filed in the United States District Court for the District of Columbia on 8 May 2001 as Civil Action Number 01-CV-0973. This lawsuit was filed in hopes of gaining injunctive relief against a moratorium on the federal funding of stem cell research. The plaintiffs in the case were seven prominent scientists who performed embryonic stem cell research and three patients: James Thomson, Roger Pedersen, John Gearhart, Douglas Melton, Dan Kaufman, Alan Trounson, Martin Pera, Christopher Reeve, James Cordy, and James Tyree. The suit was filed against Tommy G. Thompson in his official capacity as Secretary of the Department of Health and Human Services; Ruth Kirschstein in her official capacity as Acting Director of the National Institutes of Health; the Department of Health and Human Services (HHS); and the National Institutes of Health (NIH). The plaintiffs argued that by illegally delaying and withholding federal funds for stem cell research, the defendants were causing irreparable harm to research and development of potential therapies for patients.There was also concern about potentially preventing young researchers from entering the field, and restricting the sharing of discoveries between scientists that federal funding of scientific research fosters.

According to the US National Institutes of Health (NIH), the standard American source on stem cell research, three characteristics of stem cells differentiate them from other cell types: (1) they are unspecialized cells that (2) divide for long periods, renewing themselves and (3) can give rise to specialized cells, such as muscle and skin cells, under particular physiological and experimental conditions. When allowed to grow in particular environments, stem cells divide many times. This ability to proliferate can yield millions of stem cells over several months. As long as the stem cells remain unspecialized, meaning they lack tissue-specific structures, they are able to sustain long-term self-renewal.

In November 1998, two independent reports were published concerning the first isolation of pluripotent human stem cells, one of which was "Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells." This paper, authored by John D. Gearhart and his research team - Michael J Shamblott, Joyce Axelman, Shunping Wang, Elizabeith M. Bugg, John W. Littlefield, Peter J. Donovan, Paul D. Blumenthal, and George R. Huggins - was published in Proceedings of the National Academy of Science soon after James A. Thomson and his research team published "Embryonic Stem Cell Lines Derived from Human Blastocysts" in Science. Gearhart 's paper suggested that pluripotent human stem cells, which have the ability to develop into all cell types that make up the body, could be derived from primordial germ cells, which are precursors of fully differentiated germ cells, isolated from embryos. At the time, Gearhart was a professor of obstetrics and gynecology at Johns Hopkins University School of Medicine. With a background in genetics, he had devoted the majority of his research to how genes regulate tissue and embryo formation. However, the successful isolation of mice embryonic stem cells encouraged Gearhart to pursue the isolation of similar cells in humans. The principal difference between human embryonic stem (ES) cells, which Thomson 's team derived, and human embryonic germ (EG) cells, which Gearhart 's team derived, is that human embryonic germ cells are derived from early germ cells. Nonetheless, they are thought to share similar properties to human embryonic stem cells.

Stem cells are undifferentiated cells that are capable of dividing for long periods of time and can give rise to specialized cells under particular conditions. Embryonic stem cells are a particular type of stem cell derived from embryos. According to US National Institutes of Health (NIH), in humans, the term "embryo" applies to a fertilized egg from the beginning of division up to the end of the eighth week of gestation, when the embryo becomes a fetus. Between fertilization and the eighth week of gestation, the embryo undergoes multiple cell divisions. At the eight-cell stage, roughly the third day of division, all eight cells are considered totipotent, which means the cell has the capability of becoming a fully developed human being. By day four, cells begin to separate and form a spherical layer which eventually becomes the placenta and tissue that support the development of the future fetus. A mass of about thirty cells, called the inner cell mass, forms at one end of the sphere and eventually becomes the body. When the sphere and inner cell mass are fully formed, around day 5, the pre-implantation embryo is referred to as a blastocyst. At this point the cells in the inner cell mass have not yet differentiated, but have the ability to develop into any specialized cell type that makes up the body. This property is known as pluripotency. As of 2009, embryonic stem cells refer to pluripotent cells that are generally derived from the inner cell mass of blastocysts.

Nightlight Christian Adoptions et al. v. Thompson et al. was a lawsuit filed in the United States District Court for the District of Columbia on 8 March 2001. The suit was filed because Nightlight Christian Adoptions, a frozen embryo adoption agency, felt that the Guidelines for Research Using Human Pluripotent Stem Cells published by the National Institutes for Health were unlawful and violated the restrictions on human embryo research put into place by the Dickey-Wicker Amendment. Additional plaintiffs with this suit were the Christian Medical Association, adult stem cell researcher Dr. David A. Prentice, and three couples who were clients of Nightlight. The suit was filed against Tommy G. Thompson in his official capacity as Secretary of the Department of Health and Human Services; Dr. Ruth Kirschstein in her official capacity as Acting Director of the National Institutes of Health; the Department of Health and Human Services (HHS); and the National Institutes of Health (NIH).

The recent development of induced pluripotent stem cells (iPSCs) and related technologies has caught the attention of scientists, activists, politicians, and ethicists alike. IPSCs gained immediate international attention for their apparent similarity to embryonic stem cells after their successful creation in 2006 by Shinya Yamanaka and in 2007 by James Thompson and others. Although iPSCs may appear to solve the controversy over the destruction of embryos in embryonic stem cell (ESC) research by involving only the genetic reprogramming of somatic cells, further analysis of the new technique and its subsequent ethical issues could potentially lessen some ethical advantages iPSCs seemingly hold over ESCs.

Induced pluripotent stem cells (iPSCs) are studied carefully by scientists not just because they are a potential source of stem cells that circumvents ethical controversy involved with experimentation on human embryos, but also because of their unique potential to advance the field of regenerative medicine. First generated in a lab by Kazutoshi Takahashi and Shinya Yamanaka in 2006, iPSCs have the ability to differentiate into cells of all types. If scientists discover how to induce differentiated cells to return to a pluripotent state using a method that leaves the iPSCs safe for transplantation, then patients could receive stem cell transplants with cells containing their own DNA. This would presumably remove the danger of transplant rejection that comes with foreign cell transplantation.

Induced Pluripotent Stem Cells (iPSCs) are cells derived from non-pluripotent cells, such as adult somatic cells, that are genetically manipulated so as to return to an undifferentiated, pluripotent state. Research on iPSCs, initiated by Shinya Yamanaka in 2006 and extended by James Thompson in 2007, has so far revealed the same properties as embryonic stem cells (ESCs), making their discovery potentially very beneficial for scientists and ethicists alike. By avoiding the destruction of embryos and the complicated technique and resource requirements of ESCs, iPSCs may prove more practical and attractive than ESC research in the study of pluripotent stem cells.

The purpose of regenerative medicine, especially tissue engineering, is to replace damaged tissue with new tissue that will allow the body to resume normal function. The uniqueness of tissue engineering is that it can restore normal structure in addition to repairing tissue function, and is often accomplished using stem cells. The first type of tissue engineering using stem cells was hematopoietic stem cell transplantation (HSCT), a surgical procedure in which hematopoietic stem cells (HSCs) are infused into a host to treat a variety of blood diseases, cancers, and immunodeficiencies. While there is a standard procedure for the infusion of these cells into a donor, variations in the sources of hematopoietic stem cells, and in the relationship between donor and recipient, do produce some variability in the procedure.

When James Thomson of the University of Wisconsin announced in 1998 that he had derived and cultured human embryonic stem cells(hESCs), Americans widely believed-and accepted-that stem cells would one day be the basis of a multitude of regenerative medical techniques. Researchers promised that they would soon be able to cure a variety of diseases and injuries such as cancer, diabetes, Parkinson's, spinal cord injuries, severe burns, and many others. But it wasn't until January 2009 that the Food and Drug Administration approved the first human clinical trials using hESCs. The trials were put on hold in August of 2009 before they were ever begun. After more than a decade of being promised curative stem cell therapy, many people have been unwilling to wait for American doctors to provide stem cell treatments. Some people have opted not to wait or rely on other treatments, and have chosen to receive stem cell therapy from international institutions. This phenomenon has been dubbed stem cell tourism, and it has garnered much media attention, both in support and in opposition.