We will go over some basic material concerning the kinetic and diffusion approximation for the evolution of ``energy packages" of Schroedinger equations in a weak random potential. The energy package is characterized by the Wigner transform, and the evolution of this quantity has different limit behaviors on different time and spatial scales. We will emphasize the roles played by the random potential. The material presented here is extracted from works of Keller, Papanicolaou, Ryzhik, Bal, and Komorowski.