Brain blood vasculature consists of a highly ramified vessel network that is tailored for brain function.As the brain by itself does not produce vascular progenitor cells, ingression of blood vessels from surrounding perineural vascular plexus is required for continued development of brain vasculature.Although molecular mechanisms responsible for the vessel ingression into the brain and the formation of the blood-brain barrier are beginning to be elucidated, the process and its underlying mechanism by which the three-dimensional network of brain vasculature is established during development remain largely unknown.Here we report that the vasculature in the zebrafish midbrain undergoes haemodynamics-driven selective pruning from an initially exuberant interconnected meshwork to a simplified architecture that facilitates efficient arteriovenous blood flow.