Studying the function of glial cells is key to understanding how the brain works and what goes wrong in brain disease. This special issue aims to provide novel insight into glial biology and diseases. The cover of this special issue illustrates the relationship between neurogenesis and the oncogenesis of glioma, reviewed in this issue by Zhuang et al. The round ball on the cover was inspired by the traditional 'taiji太极', highlighting the transforming mechanism behind the normal and abnormal processes. Inside the ball, gliomas exist in a complicated microenvironment, including immune cells, vascular cells, and neurons, and there are special communications between neurons and glioma networks. The dragon above trying to grab the ball indicates the importance of the neurobiology of gliomas. See pages 393–408. (Cover provided by Prof. Ying Mao and Hui Yang).