Development of the central nervous system remains under strict control of the cell cycle. Spatial and temporal onset and completion of both neuro- and gliogenesis are regulated by several cell cycle proteins. Importantly, proteins comprising G1 phase regulatory network are involved in the control of stemness and/or lineage commitment balance in the pools of neural stem cells throughout the development. Deviation from this balance may lead to aberrant changes in cell division resulting in formation of brain tumour initiating cells (BTICs) which are at the source of human glioblastoma. This book provides a brief review of the cell cycle regulation at the embryonic and postnatal stages of neural development. Based on recent literature, a discussion on the role of G1 phase cyclins, cell cycle inhibitors and a novel cell cycle regulator, Spy1, in neural cell fate decisions, including mode of division and brain tumour formation, is provided in detail. The content of this book will aid in understanding how normal neural cells rely on cell cycle to control their growth and differentiation throughout life and how aberrant changes to certain cell cycle proteins contribute to gliomagenesis