Recent works [S. Gdoura and L. Guadarrama Bustos, "Transient wave imaging of anomalies: a numerical study," in Mathematical and Statistical Methods for Imaging, AMS series 548, H. Ammari et al. eds., 13pp.] on imaging of small 3-D bounded anomalies in fluid acoustics using transient (time-domain) signals are extended herein to the demanding electromagnetic case in the full Maxwell setting. Emphasis is on three items: asymptotic expressions of the scattered field (magnetic and electric) due to a spherical dielectric inclusion illuminated by an impulsive vector source, a time-reversal fomulation enabling to provide the position of this inclusion. The next step, time-reversal in somewhat attenuating media and ways to achieve it within the same wavefield framework, is underlined in conclusion