Metastasis claims 90% of all cancer-related deaths and remains clinically insuperable. The hallmarks of metastases are processes known as Epithelial to Mesenchymal Transition (EMT) and its reverse Mesenchymal to Epithelial Transition (MET) that enable primary carcinoma cells to migrate and start new tumors at distant organs. I will present an integrated theoretical and experimental approach that elucidates how cancer cells undergo EMT and MET, and how these transitions affect their ability to initiate new tumors.