The hypothetical view of a stem-cell niche. The stem-cell daughter is a CFU-S. However, if it can find and occupy a niche, it will itself become a stem cell. Figure from Schofield R. The relationship between the spleen colony-forming cell and the haemopoietic stem cell. Blood Cells. 1978;4:7-25. Reprinted with kind permission of Springer Science and Business Media.