A piece of brain tissue the size of a grain of sand contains 100,000 neurons and one billion connections—all talking to one another! You continue to make new neurons (brain cells) throughout life in response to mental activity and new learning (physical exercise helps too!).
The human brain is over three times as big as the brain of other mammals that are of similar body size. The human skull is made up of 22 bones that are joined together. Your brain is very delicate, about the consistency of soft butter. Your brain is 80 percent water. Hydration is critical to its health. The brain weighs around 3 pounds, of which 60 percent of its dry weight is fat.
Even though your brain is only 2 percent of your body's weight, it uses 20 to 30 percent of the calories you consume. Your brain uses 20 percent of the oxygen and blood flow in the body and it never rests (even during sleep).
It is thought that a yawn is your body's way of cooling down and "waking up your brain" by sending in more oxygen. There are approximately 100,000 miles of blood vessels in your brain. Your brain's "grey matter" is made up of neurons, or brain cells. Your brain's "white matter" is made up of dendrites and axons, which create the network by which neurons communicate with each other. On average, your brain is 60 percent white matter and 40 percent grey matter.
Children who learn two languages before the age of 5 have more grey matter by the time they are adults. During sleep, your cerebrospinal fluid washes away harmful waste proteins that build up between brain cells during waking hours. At times during pregnancy, the baby's brain makes 250,000 new nerve cells per minute.