The bone marrow is the major hematopoietic organ, consisting of distinct microenvironmental niches for the production of hematopoietic cells. Advanced visualizing methods are required to define and better understand the interactions between stromal and hematopoietic cells. In this chapter, we describe an ex vivo whole-mount imaging technique of the bone marrow, which allows for a fast, high-quality, and three-dimensional visualization of different bone marrow components. We provide a guide for conducting adoptive transfer experiments of fluorescently labeled leukocytes and visualizing their location in the bone marrow with respect to the bone marrow vasculature. This method presents a quick, easy, and inexpensive approach to image the bone marrow in three dimensions.