Narrow-line Seyfert 1 galaxies (NLS1s) are thought to be AGNs at the lowest mass end of supermassive black hole population and at the highest end of Eddington ratio. VLBI observations for such an extreme AGN class may provide us understanding of the dependences on these fundamental parameters of the jet-disk connection. Since the Fermi discovered gamma-ray from this class, NLS1 is now one of the hottest object. We have observed 8 radio-quiet and 6 radio- loud NLS1s using VLBA and JVN. In this talk, I present all the observational results including new preliminary ones, and several discussions based on these VLBI views of NLS1s are made.