Astronomy & Astrophysics is publishing a series of six articles presenting the results of the VLA-COSMOS 3 GHz Large Project. Led by researchers at the University of Zagreb, the team used the Karl G. Jansky Very Large Array (VLA) telescope to observe a two square degree patch of sky called the COSMOS field, for a duration of 384 hours. The astronomers obtained one of the clearest (highest angular resolution) and deepest (most sensitive) radio images ever produced over such a large region of the sky. In the radio ”skymap”, the team detected nearly 11000 galaxies. The new radio data have been combined with optical, infrared, and X-ray observations from worldwide leading telescopes.