The bone marrow niche for hematopoietic stem cells (HSCs) is a specialized microenvironment that maintains and regulates HSCs. This niche is perivascular, created by mesenchymal stromal cells and endothelial cells, and is often located near trabecular bone. The niche is complex, with functional heterogeneity among perivascular microenvironments. HSCs are found in the bone marrow, with less than 20% near the endosteum. The niche is thought to be perivascular, with HSCs maintaining proximity to blood vessels. However, the role of the endosteum and osteoblasts in niche function remains debated. Studies have shown that osteoblasts can influence HSC frequency, but direct interactions may not be necessary. The niche is regulated by multiple cell types, including endothelial cells and mesenchymal stromal cells, which produce factors like SCF and CXCL12 that support HSC maintenance. The niche also involves interactions with the sympathetic nervous system and macrophages, which regulate CXCL12 expression and HSC retention. Other factors, such as Pleiotrophin and Robo4/Slit2, also play roles in niche function. The niche is complex, with distinct regions and functions, and further research is needed to fully understand its components and regulation. The niche is essential for HSC maintenance and hematopoiesis, and understanding it may lead to new approaches for treating hematologic disorders.The bone marrow niche for hematopoietic stem cells (HSCs) is a specialized microenvironment that maintains and regulates HSCs. This niche is perivascular, created by mesenchymal stromal cells and endothelial cells, and is often located near trabecular bone. The niche is complex, with functional heterogeneity among perivascular microenvironments. HSCs are found in the bone marrow, with less than 20% near the endosteum. The niche is thought to be perivascular, with HSCs maintaining proximity to blood vessels. However, the role of the endosteum and osteoblasts in niche function remains debated. Studies have shown that osteoblasts can influence HSC frequency, but direct interactions may not be necessary. The niche is regulated by multiple cell types, including endothelial cells and mesenchymal stromal cells, which produce factors like SCF and CXCL12 that support HSC maintenance. The niche also involves interactions with the sympathetic nervous system and macrophages, which regulate CXCL12 expression and HSC retention. Other factors, such as Pleiotrophin and Robo4/Slit2, also play roles in niche function. The niche is complex, with distinct regions and functions, and further research is needed to fully understand its components and regulation. The niche is essential for HSC maintenance and hematopoiesis, and understanding it may lead to new approaches for treating hematologic disorders.