Mind & EverydayFact
You don't use 10 percent of your brain. You use all of it.
Imaging shows activity across all brain regions, including during sleep. The brain is about 2 percent of body weight but burns roughly 20 percent of your energy – 90 percent idle tissue would be evolutionarily absurd. Even small damage to small regions causes clear deficits.
Useful: Anything promising to unlock your "unused 90 percent" is selling you a legend.
Source: en.wikipedia.org