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The control of lifelong persistence of hematopoiesis is exerted by hematopoietic stem cells (HSCs) in specialized microenvironments called “hematopoietic niches,” through molecular cues that are only partially understood. Agrin, a proteoglycan known to play essential roles in the regulation of the neuromuscular junction, is a critical component of the bone marrow hematopoietic niche. In mice, agrin is expressed by multipotent nonhematopoietic mesenchymal stem cells (MSCs) and differentiated osteoblasts lining the endosteal bone surface, and it provides signals necessary for the survival and differentiation of CD34⁺CD135⁻ LSK cells. This picture is the confocal image of a methapyseal section of leg bones where osteoblasts are stained for osteopontin (red), agrin (green), and nuclear DNA (blue). See the article by Mazzon et al on page 2733.