Every simply connected, closed 3manifold is homeomorphic to the 3sphere. Stated above is what mathematical problem named for a Frenchman that defied experts for a century before it was solved by Grigori Perelman in 2006?
Answer: PoincarĂ© conjecture
The page lists evidence documents from Wikipedia.
Wikipedia documents 

3manifold  Wikipedia

3sphere  Wikipedia

Grigori Perelman  Wikipedia
