Control of osteogenesis by the canonical Wnt and BMP pathways in vivo: The cover image shows a transverse section through a Xenopus tropicalis metamorphosing tadpole phalange. This histological section was stained with Kernechtrot to reveal cell bodies (pink) and Alcian blue to show the cartilage (blue). The circular cartilaginous shaft is surrounded by a layer of bone mineralized matrix (grey ring) secreted by adjacent osteoblasts. On pages 953–962 Marcellini et al. review recent experimental evidence showing that the canonical Wnt and BMP pathways functionally interact as cells differentiate from osteochondroprogenitors to osteoblasts and osteocytes, in the context of the developing vertebrate embryo. BMP signalling specifies multipotent mesenchymal cells into osteochondroprogenitors which are subsequently driven towards the osteoblastic fate by the Wnt pathway. In osteoblasts, both pathways promote differentiation, albeit with notable mechanistic differences. Finally, in osteocytes, the Wnt and BMP pathways exert opposite effects on the control of bone resorption by osteoclasts.