  The role of magnetic fields for the formation of planets is reviewed.
Protoplanetary disc turbulence driven by the magnetorotational instability has
a huge influence on the early stages of planet formation. Small dust grains are
transported both vertically and radially in the disc by turbulent diffusion,
counteracting sedimentation to the mid-plane and transporting crystalline
material from the hot inner disc to the outer parts. The conclusion from recent
efforts to measure the turbulent diffusion coefficient of magnetorotational
turbulence is that turbulent diffusion of small particles is much stronger than
naively thought. Larger particles -- pebbles, rocks and boulders -- get trapped
in long-lived high pressure regions that arise spontaneously at large scales in
the turbulent flow. These gas high pressures, in geostrophic balance with a
sub-Keplerian/super-Keplerian zonal flow envelope, are excited by radial
fluctuations in the Maxwell stress. The coherence time of the Maxwell stress is
only a few orbits, where as the correlation time of the pressure bumps is
comparable to the turbulent mixing time-scale, many tens or orbits on scales
much greater than one scale height. The particle overdensities contract under
the combined gravity of all the particles and condense into gravitationally
bound clusters of rocks and boulders. These planetesimals have masses
comparable to the dwarf planet Ceres. I conclude with thoughts on future
priorities in the field of planet formation in turbulent discs.
