This study investigates the distinct niches occupied by haematopoietic stem cells (HSCs) and early lymphoid progenitors in the bone marrow. Using genetic and molecular techniques, the researchers identified that HSCs reside in a perivascular niche, while early lymphoid progenitors are located in an endosteal niche. The chemokine CXCL12, crucial for HSC maintenance, is primarily produced by perivascular stromal cells and endothelial cells. Conditional deletion of CXCL12 from these cells led to HSC depletion, whereas deletion from osteoblasts affected early lymphoid progenitors but not HSCs. The study also showed that SCF, another key factor for HSC maintenance, is expressed by perivascular stromal cells and endothelial cells. Deletion of SCF from these cells also depleted HSCs. These findings suggest that HSCs and early lymphoid progenitors occupy distinct niches in the bone marrow, with HSCs relying on perivascular stromal cells and endothelial cells, while early lymphoid progenitors depend on osteoblasts. The study highlights the importance of specific cellular environments in maintaining different haematopoietic cell populations.This study investigates the distinct niches occupied by haematopoietic stem cells (HSCs) and early lymphoid progenitors in the bone marrow. Using genetic and molecular techniques, the researchers identified that HSCs reside in a perivascular niche, while early lymphoid progenitors are located in an endosteal niche. The chemokine CXCL12, crucial for HSC maintenance, is primarily produced by perivascular stromal cells and endothelial cells. Conditional deletion of CXCL12 from these cells led to HSC depletion, whereas deletion from osteoblasts affected early lymphoid progenitors but not HSCs. The study also showed that SCF, another key factor for HSC maintenance, is expressed by perivascular stromal cells and endothelial cells. Deletion of SCF from these cells also depleted HSCs. These findings suggest that HSCs and early lymphoid progenitors occupy distinct niches in the bone marrow, with HSCs relying on perivascular stromal cells and endothelial cells, while early lymphoid progenitors depend on osteoblasts. The study highlights the importance of specific cellular environments in maintaining different haematopoietic cell populations.