  Recent observations have suggested that circumstellar disks may commonly form
around young stellar objects. Although the formation of circumstellar disks can
be a natural result of the conservation of angular momentum in the parent
cloud, theoretical studies instead show disk formation to be difficult from
dense molecular cores magnetized to a realistic level, owing to efficient
magnetic braking that transports a large fraction of the angular momentum away
from the circumstellar region. We review recent progress in the formation and
early evolution of disks around young stellar objects of both low-mass and
high-mass, with an emphasis on mechanisms that may bridge the gap between
observation and theory, including non-ideal MHD effects and asymmetric
perturbations in the collapsing core (e.g., magnetic field misalignment and
turbulence). We also address the associated processes of outflow launching and
the formation of multiple systems, and discuss possible implications in
properties of protoplanetary disks.
