Brain tumor tissue can be hard to distinguish from normal brain during surgery. Neurosurgeons use their best judgment in the operating room but often have to guess exactly where the edges of the tumor are while removing it. A new laser-based microscopic technology may help surgeons see the difference between tumor tissue and normal brain in real-time. Called a stimulated Raman scattering (SRS) microscope, it’s now being tested at the University of Michigan Health System. Images collected using an SRS microscope show that normal brain contains sparse cells with bundles of nerve fibers, called axons, but brain tumor tissue is full of cells in a disordered pattern.