Henri Poincaré asked, in the year 1904, whether every simply connected closed three dimensional manifold is homeomorphic to the 3-dimensional sphere. The assertion that it is so is known as Poincaré conjecture. It was finally solved a hundred years later by Grigori Perelman who was awarded the Fields Medal in the Madrid ICM-2006. In this talk we give an overview of the development in Topology around this conjecture.
