What is the history of research on adult stem cells?

The history of research on adult stem cells began about forty years ago. In the 1960s, researchers discovered that bone marrow contains at least two kinds of stem cells. One group, called hematopoietic stem cells, forms all the types of blood cells in the body: red blood cells, B lymphocytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, macrophages, and platelets. The second group, called bone marrow stromal cells, was discovered a few years later. They can generate bone, cartilage, fat, and fibrous connective tissue.

Also in the 1960s, scientists who were studying rats discovered two regions of the brain that contained dividing cells, which become nerve cells. But it was not until the 1990s that scientists found the adult brain does contain three stem cell types - astrocytes, oligodendrocytes, and neurons, or nerve cells.