The fusion of cells is a fundamental biological event that is essential for a variety of developmental and homeostatic processes. Fusion is required for the formation of multinucleated osteoclasts and giant cells, although the mechanisms that govern these processes are poorly understood. A new study now reveals an unexpected role for the receptor, dendritic cell-specific transmembrane protein (DC-STAMP), in this process. The potential mechanism by which DC-STAMP governs fusion and the implications of this finding will be discussed.