The images show a typical vascularized tumor tissue with cancer cells (unlabeled), collagen matrix (purple/white) and blood vessels (red). A novel strategy to fight cancer is to use tumor-seeking bacteria that can be modified to produce and release cancer toxins. A certain type of bacteria can even produce little magnetic particles in their body that make them respond to external magnetic fields, and also allow us to track them in the body using MRI. We study how such living therapeutic microorganisms (green/yellow) move in these vessels and how we can help them go deeper into the tissue using dynamic magnetic fields to make therapy become more effective.