Some 10 % of cancer patients develop metastases in the brain – often long after successful treatment of the primary tumor. In such cases, the prognosis is generally poor. The mechanisms responsible for the appearance of brain metastases have long been mysterious. Now a research team led by LMU neurologists Dr. Frank Winkler and Professor Jochen Herms has followed, in real time, the multistep process that enables cancer cells to establish metastases, and seen that many of them get stuck along the way.