  Narrow-line Seyfert 1 galaxies, with their extreme properties, defy our
current knowledge of active galactic nuclei and relativistic jet systems. They
excite, and might help us answer, many questions concerning the evolution and
unification of AGN, but still remain a poorly studied class of AGN as such.
  We did an extensive study of a large sample of NLS1s using various
statistical methods, for example, multiwavelength correlations and principal
component analysis. We wanted to examine how and where in NLS1s different kinds
of radiation are produced, and how the emission properties are connected to
other intrinsic AGN properties. In addition we present the early results of our
ongoing research about the large-scale environments of NLS1s. We also introduce
the Mets\"ahovi Radio Observatory NLS1 survey and its first results, and show
some early results for individual sources.
