Using scanning electron microscopy with polarization analysis (SEMPA) we directly observed domain wall distortions, transitions between vortex and transverse wall sates, and defect-to-defect hopping of domain walls while flowing current through narrow ferromagnetic wires. These current induced effects on domain walls are the result of the quantum mechanical phenomenon of spin transfer torque. Spin transfer torque in domain walls is fundamentally related to the conservation of angular momentum as spin polarized electrons change their spin orientation while passing through the wall. The resulting “spin pressure” pushes the wall in the direction of the electron flow, leading to domain wall motion. The observed domain wall distortions, transitions, and interactions with defects are all expected to play a significant role in spin torque driven magneto-electronics.