Recent years have seen tremendous progress in our understanding of angular momentum transport in protoplanetary disks. It is now thought that accretion is driven primarily by a large-scale vertical field threading the disk, either through magnetically launched winds or large-scale magnetic stresses within the disk plane. However, it remains an open question as to just how laminar these accreting disks are. Even if not the primary source of angular momentum transport, turbulence may still play a crucial role in the multitude of processes involved in forming planets.
In this talk, I will present both theoretical and observational evidence that protoplanetary disks are not necessarily laminar and in some cases can still harbor vigorous turbulence. From ALMA observations of molecular line broadening, we now know of at least one source that presents a clear signature of turbulence. I will present these compelling new observations and compare them to earlier predictions of magnetically driven turbulence. I will also present a number of numerical experiments that indeed show magnetically driven turbulence is still present throughout large regions of the disk, even in the presence of a large-scale magnetic field. I will conclude with an outlook for future observational and theoretical studies and what the results so far imply for our understanding of planet formation and disk evolution.