Question: What substance makes up roughly 75% of the human brain?
Answer: Our brains are mostly water. To be specific, the human brain is made up of 73–75% water, 10–12% fat, and small amounts of cholesterol, proteins, carbohydrates, minerals, and salts. Cholesterol may be surprising to see on the list, but it plays an important role in building brain cells and supporting communication between neurons.
