The hematopoietic system is organized in a hierarchical manner. Hematopoietic stem cells reside at the top of the hematopoietic system and give rise to all mature blood and immune cells through a hierarchical process of cell lineage commitment. HSCs also have the ability of regenerating themselves through so-called self-renewal. The key functional outcome of these characteristics is that life-long multipotent self-renewing HSCs give rise to long term multilineage repopulation in transplantation settings. Hematopoiesis takes place in the bone marrow and is regulated by both intrinsic and extrinsic factors. A major interest in the lab is to identify what these factors are, and to investigate how they contribute to HSC regulation.