3. Christopher Hirata

The phenomenal IQ (225) of this 31-year old Japanese-American astrophysicist lands him third in this list. At the age of 12, Christopher Hirata already pursued college-level courses (calculus and physics), around the time most of us were just in the 7th grade. At the age of 13, this whiz kid became the youngest American to have ever won the gold medal in the 1996 International Physics Olympiad.
At 16, he was already working with NASA on its ambitious project to conquer Planet Mars. After he procured his Ph.D. at the Princeton University, he went back to California Institute of Technology, where he is currently teaching astrophysics.