Haematopoietic stem cells (HSC) are characterised by a flexible potential to proliferate, to produce large numbers of differentiated cells, to self-renew their own population, and to regenerate the functional tissue after injury [7,8]. Although these capabilities are well defined, the mechanisms underlying the regulation and control of stem cell proliferation, differentiation, and self-renewal are still unknown. In contrast to the high experimental effort to investigate these processes only little progress has been made to establish a theoretical framework of stem cell organisation.