  Recent high-resolution observations from the Solar Dynamics Observatory (SDO)
have reawakened interest in the old and fascinating phenomenon of solar
tornado-like prominences. This class of prominences was first introduced by
Pettit (1932), who studied them over many years. Observations of tornado
prominences similar to the ones seen by SDO had already been documented by
Secchi (1877) in his famous "Le Soleil". High resolution and high cadence
multiwavelength data obtained by SDO reveal that the tornado-like appearance of
these prominences is mainly an illusion due to projection effects. We discuss
two different cases where prominences on the limb might appear to have a
tornado-like behavior. One case of apparent vortical motions in prominence
spines and barbs arises from the (mostly) 2D counterstreaming plasma motion
along the prominence spine and barbs together with oscillations along
individual threads. The other case of apparent rotational motion is observed in
prominence cavities and results from the 3D plasma motion along the writhed
magnetic fields inside and along the prominence cavity as seen projected on the
limb. Thus, the "tornado" impression results either from counterstreaming and
oscillations or from the projection on the plane of the sky of plasma motion
along magnetic field lines, rather than from a true vortical motion around an
(apparent) vertical or horizontal axis. We discuss the link between
tornado-like prominences, filament barbs, and photospheric vortices at their
base.
