Because their internal as well as their external degrees of freedom can be very well controlled, cold atoms make it possible to experimentally study a number of fundamental physical processes for quantum disordered systems or few/many-body interacting systems, such as ballistic/diffusive transport, and phenomena due to quantum interference between multiple scattering paths, such as weak localization, coherent back-scattering and strong (a.k.a. Anderson) localization. In 3D, there is a metal/insulator transition in strong disorder, which can be studied using cold atoms exposed to a disordered optical potential created by a laser speckle. We show that the unusual statistical properties of speckle potentials are responsible on the one hand for large deviations from the predictions of the self-consistent theory of localization, and on the other hand to unexpected difficulties in interpreting the experimental results.