Millions of people worldwide are diagnosed with cancer every year. In advanced tumor diseases, cancer cells detach from the original tumor and settle in other parts of the body to form metastases. On their way, they have to be distributed via the body’s own transport system, such as blood or the lymphatic vascular system, and overcome numerous mechanical hurdles. A multidisciplinary research team has investigated how the mechanical properties of tumor cells circulating through blood vessels influence their metastatic pathways. The results, recently published in Nature Materials, provide important building blocks for understanding metastasis.