The majority of the human brain is composed of water, which constitutes about 75% of its total weight. Additionally, the brain is made up of neurons and glial cells, with grey matter containing the cell bodies and white matter consisting of myelinated axons. The brain's high water content is crucial for maintaining its structure, facilitating communication between neurons, and supporting metabolic processes. Overall, the brain's intricate architecture and cellular composition enable it to perform essential functions, including cognition, sensory processing, and coordination of bodily activities.