James Till & Ernest McCulloch
Discovered stem cells · 1960s
James Till and Ernest McCulloch developed quantitative experiments in irradiated mice showing that transplanted bone-marrow cells could form discrete spleen colonies. The work helped establish functional, clonal approaches to studying blood-forming progenitors and became foundational to experimental haematopoietic stem-cell biology.
The historical assay addressed colony-forming and self-renewal questions in a defined animal system; it should not be used to validate unrelated commercial cell products. Read the 1962 radiation-sensitivity paper and a modern account of the CFU-S assay.
Most clinical uses of stem cells remain investigational — check the evidence and approval status for your condition before acting on any clinic's claims.