In this research project the evolution of highly malignant primary brain tumors is investigated. These tumors are the result of an evolutionary process that is driven by randomly acquired mutations and selection. They consist of a heterogeneous population of cell clones that develop differently over time. New sequencing techniques and mathematical models are used to study these clones. In this way, the selective advantage of individual mutations can be identified and the growth dynamics of subclones determined. A comprehensive understanding of these processes is crucial for treating brain tumors more effectively.