Cerebrospinal fluid (CSF) is a transparent-clear, colorless, and opac fluid within the brain and spinal cord’s ventricles and subarachnoid space. It plays a crucial role in the central nervous system (CNS), providing mechanical protection, maintaining homeostasis, and facilitating the removal of metabolic waste. The choroid plexus produces the CSF primarily in the brain ventricles, circulating through the ventricular system before reabsorbing into the bloodstream via the arachnoid granulations. The brain produces about 500 ml of CSF every day. At birth, the human ventricular volume is usually 150 ml, and an absent CSF or deformity of the ventricles can lead to serious neurological problems for the infant. The volume of the ventricle decreases to 30 ml as an adult. The ventricles are filled with CSF, and these ventricles are expanded as water balloons and contain relatively low-density objects (part of the cranium is removed to show the shape of the ventricles). The CSF-contacting cells on the surface of the brain’s ventricular system are essential for the normal functioning of the CNS, and their roles include CSF circulation, the removal/transportation of substances and cells between CSF and brain tissue, control or regulation of the CNS, and receptor function. The CNS and digestive system are the only two systems where the fluid flows directionally. It is well known how water moves from the intestinal wall to PMC (Peyer’s patch containing M cells) and from the blood to the CSF. However, it is poorly understood how CSF, interstitial fluid, lymphatic fluid, and blood, and so on can provide directions of communication and exchange between the blood-brain barrier, glia limitants, subarachnoid villi, septal barrier, circumventricular organ, circumventricular sub-center, CSF-contacting receptors, and brain interstitial fluid. nThe composition of CSF is tightly regulated, with alterations often indicating neurological conditions such as infections, hemorrhages, and tumors. Diagnostic analysis of CSF includes examining its pressure, cellular content, protein levels, and biochemical markers, which can provide critical insights into CNS pathologies. Advances in CSF research have enhanced the understanding of its role in neurodegenerative diseases, offering potential biomarkers for early diagnosis and monitoring of diseases such as Alzheimer’s and Parkinson’s.nCSF dynamics and its interaction with brain interstitial fluid are active research areas with implications for developing therapeutic strategies for CNS disorders. Understanding the complexities of CSF physiology and pathology remains essential for advancing neurological science and clinical practice.