Topological insulators (TIs) have attracted great attention from both the theoretical and technology aspects due to the large spin-orbit coupling, altering the topology of the energy bands.They can be grown layer-by-layer by molecular beam epitaxy.TI also offers the unique opportunity for engineering spin orbit coupling a new tool box for special relativity.The resulting surface Dirac electrons are protected from backscattering and thus, offer high mobility and dissipationless quantum spin Hall.With breaking of time reversal symmetry by magnetic doping, dissipation-less transport may be achieved without applied magnetic field.It also offers potentials for constructing low dissipation devices and technology.In addition, the manipulation of surface state magnetism is also shown to be able to offer an extraordinary large spin orbit torque and thus offer a tremendous potential for constructing efficient magnetic switching.