Abstract
The blood-brain barrier (BBB) protects the central nervous system (CNS) from potentially harmful substances and molecules by limiting their influx from the blood stream into the brain parenchyma. Understanding the structure and functioning of the BBB is of major importance for the development of effective medical treatments for primary and secondary brain tumours. Therefore, we provide here a concise and illustrated educational description of the anatomy and physiology of the BBB and current concepts on its role for targeted cancer therapies and immuno-oncology.