Bone-dissolving cells called osteoclasts are derived from a type of immune cells called macrophages. They are necessary for the maintenance and renewal of bones. But the intracellular mechanisms through which macrophages convert to osteoclasts are not fully understood. Recently, scientists have uncovered the role of a protein called Cpeb4 in this process. Their findings suggest potential therapeutic targets for bone and joint diseases like arthritis and osteoporosis.