  It is very likely that in 3-4 years the construction of one or two linear
colliders with c.m.s energy up to 0.5--1.5 TeV will be started. Besides e^+e^-
collisions, linear colliders give a unique possibility to study gamma-gamma and
gamma-electron interactions at energies and luminosities comparable to those in
e^+e^- collisions. High energy photons for gamma-gamma and gamma-electron
collisions can be obtained using laser backscattering. These types of
collisions considerably increase the physics potential of linear colliders for
relatively a small incremental cost. This report briefly reviews the physics
goals and possible parameters of gamma-gamma colliders.

High Energy Physics - Experiment;High Energy Physics - Phenomenology;Accelerator Physics;Optics