Using numerical simulations, our group explores the effect of magnetic fields on disk formation, evolution, substructure, and grain growth within the disks. The relative strengths of non-ideal MHD effects determine whether a disk can form at all, as well as the orientation of the disk. Ambipolar diffusion, one important non-ideal MHD effect, removes small grains from the disk, which in turn changes the ambipolar diffusivity and promotes disk formation. The growth of larger grains also depends on the magnetic field: the magneto-rotational instability generates turbulence in the disk, which can result in much faster grain growth compared to the hydrodynamic Kolmogorov turbulence. Finally, the interplay between the magnetic field and the grain growth creates a wealth of substructures in the disks, carving out gaps and rings, where planet formation may occur.