Bone homeostasis is regulated by communication between bone-forming mature osteoblasts (mOB) and bone-resorptive mature osteoclasts (mOC). However, the interaction between them in vivo remains unclear. Researchers have developed an intravital two-photon microscopy technique which reveals mOB and mOC functions are regulated via direct cell-cell contact between these cell types. The findings may pave the way for the development of new therapies for diseases such as osteoporosis and cancer bone metastasis.