IACOB is an ambitious long-term observational project with a main scientific goal: providing an unprecedented empirical overview of the main physical properties of Galactic massive O- and B-type stars which can be used as definitive anchor point for our theories of stellar atmospheres, winds, interiors and evolution of massive stars. Apart from exploiting the high performance of the FIES and HERMES high-resolution spectrographs attached to the NOT and Mercator telescopes in the Canary Islands' observatories, the IACOB project has spent more than 1000 hours of SONG time since December 2014. In this talk I will explain the scientific interest of the compilation and exploitation of this unique spectroscopic dataset.