People die from breast cancer when it metastasizes and spreads throughout the body. Clinicians and scientists do not fully grasp how metastatic disease spreads and forms. In order to develop better treatments for people with metastatic breast cancer, we need better research tools. Specifically, we need better experimental models that will enable us to capture how metastatic cells move throughout the body and dynamically interact with the immune system. Our lab is focused on using these tools to understand how metastatic cancer cells can leave the breast and end up growing in different organs. Critical to understanding how this process unfolds will be determining how our immune system fails to kill these spreading cancer cells.