Microglial cells are the sessile immune cells of the central nervous system (CNS). During early postnatal stages, they immigrate from the peripheral blood into the brain tissue and keep many physiological features of peripheral monocytes . In the healthy brain, microglial cells are characterized by a ramified morphology and are termed resting microglia. Microglia continuously monitor the well-being of the CNS. During any kind of disease or any pathological event such as after trauma, stroke or brain tumor growth, the resting microglial cell transforms into an activated form - characterized by an ameboid morphology. Activated microglia proliferate and migrate to the site of injury where they phagocytose pathogens or damaged cells and release of a variety of factors like cytokines, chemokines, nitric oxide and growth factors e.g. to coordinate immune responses. However, in gliomas microglia have an adverse role. Microglial cells are attracted towards glioma in large numbers and consequently glioma tissue consists up to 30% of microglial cells. Microglia density in gliomas positively correlates with malignancy, invasiveness and grading of the gliomas.