Abstract. We give an overview of circumstellar interaction in young Type II supernovae, as seen through the eyes of verylong-baseline interferometry (VLBI) observations. The resolution attained by such observations ( < ∼ 1 mas) is a powerful tool to probe the interaction that takes place after a supernova goes off. The direct imaging of a supernova permits, in principle, to estimate the deceleration of its expansion, and to obtain information on the ejecta and circumstellar density profiles, as well as estimates of the magnetic field intensity and relativistic particle energy density in the supernova. Unfortunately, only a handful of radio supernovae are close and bright enough as to permit their study with VLBI. We present results from our high-resolution observations of the nearby Type II radio supernovae SN 1986J and SN 2001gd
