A study published in *Nature* (481(7382): 457–462. doi:10.1038/nature10783) reveals that endothelial and perivascular cells maintain hematopoietic stem cells (HSCs) in the bone marrow. The research shows that stem cell factor (SCF) is primarily expressed by perivascular cells and is essential for HSC maintenance. When SCF was conditionally deleted from endothelial cells or Lepr-expressing perivascular stromal cells, HSCs were significantly depleted. In contrast, deletion of SCF from hematopoietic cells, osteoblasts, or Nestin-expressing cells did not affect HSC frequency or function. The study also found that SCF is non-cell-autonomous, with membrane-bound SCF playing a critical role in HSC maintenance. SCF is expressed by endothelial cells, perivascular stromal cells, and mesenchymal stem cells, but its source in the HSC niche remains unclear. The research demonstrates that endothelial and perivascular stromal cells are major sources of SCF for HSC maintenance, and their deletion leads to significant HSC depletion. The findings suggest that HSCs reside in a perivascular niche where multiple cell types contribute to their maintenance. The study highlights the importance of endothelial and perivascular cells in supporting HSC function and underscores the need for further research to fully understand the complex interactions within the HSC niche.A study published in *Nature* (481(7382): 457–462. doi:10.1038/nature10783) reveals that endothelial and perivascular cells maintain hematopoietic stem cells (HSCs) in the bone marrow. The research shows that stem cell factor (SCF) is primarily expressed by perivascular cells and is essential for HSC maintenance. When SCF was conditionally deleted from endothelial cells or Lepr-expressing perivascular stromal cells, HSCs were significantly depleted. In contrast, deletion of SCF from hematopoietic cells, osteoblasts, or Nestin-expressing cells did not affect HSC frequency or function. The study also found that SCF is non-cell-autonomous, with membrane-bound SCF playing a critical role in HSC maintenance. SCF is expressed by endothelial cells, perivascular stromal cells, and mesenchymal stem cells, but its source in the HSC niche remains unclear. The research demonstrates that endothelial and perivascular stromal cells are major sources of SCF for HSC maintenance, and their deletion leads to significant HSC depletion. The findings suggest that HSCs reside in a perivascular niche where multiple cell types contribute to their maintenance. The study highlights the importance of endothelial and perivascular cells in supporting HSC function and underscores the need for further research to fully understand the complex interactions within the HSC niche.