Abstract
Steady-state hematopoietic stem cells' (HSCs) self-renewal and differentiation toward their mature progeny in the adult bone marrow is tightly regulated by cues from the microenvironment. Recent insights into the cellular and molecular constituents have uncovered a high level of complexity. Here, we review emerging evidence showing how HSCs and their progeny are regulated by an interdependent network of mesenchymal stromal cells, nerve fibers, the vasculature, and also other hematopoietic cells. Understanding the interaction mechanisms in these intricate niches will provide great opportunities for HSC-related therapies and immune modulation.