Abstract: Recent high-resolution ALMA observations have revealed many interesting
features in protoplanetary disks (PPDs), many of which are associated with dust-gas 
interactions in such disks. Understanding such interactions will not only provide
better constraints on our knowledge of the physical conditions in PPDs, but also
yield conditions that are conducive for planetesimal formation. We present high-resolution
2D and 3D disk gas-dust simulations to examine several instabilities associated with
dust, including shearing instability, vertical shear instability and Rossby wave instability.
We also explore the implications of such dynamics on explaining the ALMA observations
as well as processes for protoplanet formation.