iClusters (red/blue/green circles) enter a tumor through the bloodstream (red vessels), then disassemble into smaller nanoparticle drugs (blue circles) that can pass through lymphatics (green vessels) into lymph nodes and kill metastases.Metastasis, in which cancer cells break free from the primary tumor and form tumors at other sites, worsens the prognosis for many cancer patients. The lymph nodes –– glands of the immune system located throughout the body –– are typically the traveling cells’ first destination. Now, researchers have developed a strategy to target metastases in lymph nodes for destruction, before they can cause cancer at other locations. They report their results in ACS Nano.