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Spatiotemporal magnetization reversal dynamics in a Ni 80 Fe 20 microstructure is studied using ps time scale scanning Kerr microscopy. Time domain images reveal a striking change in the reversal associated with the reduction in switching time when a transverse bias field is applied. Magnetization oscillations subsequent to reversal are observed at two resonance frequencies, which sensitively depend on the bias field strength. The oscillation at f= 2 GHz is caused by the damped precession of M, while the lower frequency∼ 0.8 GHz mode is interpreted in terms of domain wall oscillation.