Wave Turbulence Theory describes systems with a large number of dispersive and interacting waves. A most remarkable feature of the theory is its universal prediction of the Wave Kinetic Equation (WKE), which is an evolution equation for the energy density. In this talk we will present the theory and the Wave Kinetic Equation for the Nonlinear Schrödinger equation. We will discuss recent progress made in understanding wave turbulence and the many remain challenges.