  Anisotropic flow is recognized as one of the main observables providing
information on the early stage of a heavy-ion collision. At RHIC the large
observed anisotropic flow and its successful description by ideal hydrodynamics
is considered evidence for an early onset of thermalization and almost ideal
fluid properties of the produced strongly coupled Quark Gluon Plasma. This
write-up discusses some key RHIC anisotropic flow measurements and for
anisotropic flow at the LHC some predictions.
