The extracellular space in brain cells is an ultra-microstructure that has not been fully understood. It not only provides the fundamental conditions and environment required for the functional activity of neurons and neural networks, but the molecular transport within it also plays a critical role in essential brain functions such as sleep, memory, and sensory formation. Due to its nano-scale structure and the difficulty in in vivo detection, it has not been thoroughly studied. This academic exchange will introduce and compare various techniques for probing the extracellular space of brain cells, summarize the latest scientific discoveries regarding this space, and, in conjunction with reports on the patterns and influencing factors of molecular transport within this space, discuss the feasibility of establishing novel neuro-modulatory theories and technological systems based on the extracellular space. Additionally, this session will provide a future outlook on brain disease treatments via pathways through the extracellular space.