Contents 1. Polynomial Approximation and the Taylor Tower 3 2. The Classification of Homogeneous Functors 8 3. The Taylor Tower of the Identity Functor for Based Spaces 10 4. Operads and Tate Data: the Classification of Taylor Towers 17 5. Applications and Calculations in Algebraic K-Theory 23 6. Taylor Towers of Infinity-Categories 26 7. The Manifold and Orthogonal Calculi 28 8. Further Directions 32 References 33Goodwillie calculus is a method for analyzing functors that arise in topology. One may think of this theory as a categorification of the classical differential calculus of Newton and Leibnitz, and it was introduced by Tom Goodwillie in a series of foundational papers [45, 46, 47].The starting point for the theory is the concept of an n-excisive functor, which is a categorification of the notion of a polynomial function of degree n. One of Goodwillie's key results says that every homotopy functor F has a universal approximation by an n-excisive functor P n F , which plays the role of the n-th Taylor approximation of F . Together, the functors P n F fit into a tower of approximations of F : the Taylor tower