He is considered by some to be the smartest man alive. He has attacked mathematics problems that have eluded others and made progress in frighteningly short periods of time. He won the Fields Medal in 2006, for work he had done before age 30 - though it should be noted that mathematicians often show their best work early.
Yet knowing more about him, it raises questions about what "smart" is. He confessed great relief at getting to a level of education while still very young where he didn't have to do anything but mathematics. To the school writing assignment "What has been going on at your house lately?" he could only manage to list the objects in his home. Fascinating to think about, really.
He has made unexpected progress on a problem that other mathematicians warn each other away from, because of its deceptive simplicity. Many brilliant minds have crashed up against the rocks of this question, apparently. I like this discussion of the problem, because I have enough numbers-obsession and understanding of integer trends and relationships to dimly grasp what is happening and why it might swallow a beautiful mind whole, yet can still appreciate that understanding is far beyond me. The graphic of the mathematical progression that tops the article is worth string at for many minutes. If you like that sort of thing, that is. It softly instructs me to come over to the Dark Side to fulfill my destiny. Many of those numbers are friend of mine.
He attacked from an angle that shows almost no chance of getting to an ultimate proof, yet gets much farther on a practical level than any others have previously managed. That in itself takes a certain sort of brilliance, to realise when perfection is not going to be available, but half a loaf - or in this case 99.99% of a loaf - is available elsewhere.