+The Poincaré Conjecture, a central puzzle in [Topology](/wiki/topology), proposed that any simply connected, closed 3-dimensional [Manifold](/wiki/manifold) is topologically a 3-sphere. This profound idea, concerning the fundamental shape of space, remained unsolved for a century before its celebrated proof.
+## See also
+- [Geometry](/wiki/geometry)
+- [Proof](/wiki/proof)
+- [Perelman](/wiki/perelman)
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