The study of star formation is extremely challenging due to the lack of complete and clean samples of young, nearby clusters, and star forming regions. The recent Gaia DR2 catalogue complemented with the deep, ground based COSMIC DANCe catalogue offers a new database of unprecedented accuracy to revisit the membership of clusters and star forming regions. I will present recent results characterizing young open clusters and star forming regions in terms of the mass function and the spatial distribution. Finally, I will expose the spectroscopic follow-up programs we are carrying on in these regions.