As occurs in any other vascularized organ, one of the essential functions of blood vessels in bone is to be a source of O2, nutrients, hormones and growth factors (1). However, additional roles for bone blood vessels are emerging. For example, osteoblast precursors have been recently identified within their wall (2,3), which suggests that blood vessels are a source of osteoprogenitors. Moreover, it has been shown that endothelial cells are specialized niches for hematopoietic stem cells (4,5). In light of these findings, identification of the molecular and cellular mechanisms controlling angiogenesis in bone is essential in order to reach a full understanding of how bone and bone marrow development and homeostasis are regulated.