Perelman will give a special Colloquium talk on Thursday April 17 at 5:30 pm in A5: "The entropy formula for the Ricci flow and its geometric applications" Perelman claims to have solved the Poincare Conjecture, in fact a much stronger conjecture due to Thurston, called the Geometrization Conjecture for 3-manifolds. I will give a pre-talk for the graduate students that explains some of the terminology involved and how it implies the Poincare Conjecture.