| Citation | Professor Till founded with McCulloch the field of modern haemotology by demonstrating the existence of stem cells that give rise to all blood cell types . They devised the first spleen colony assay for blood cell precursors and used it to demonstrate that these stem cells have the properties of self-renewal, proliferation and multilineage differentiation. Using irradiation-induced chromosome breaks to follow individual precursor cells and their progeny, they demonstrated that each spleen colony was a clone. Their contributions laid the foundation for the isolation of stem cells for bone marrow transplantation and much else besides |