Metastases that form in the bone constitute an essentially untreatable disease, so understanding the mechanisms that enable this is crucial. This paper indicates that platelets might function as messengers that exchange information between the primary tumour and the bone microenvironment. Specifically, primary tumours in mice can induce bone formation. The depletion of platelets in three mouse cancer models prevented bone formation, and the authors found that platelets can sequester proteins such as transforming growth factor-β that result in changes to the bone microenvironment.