Observations reveal that star formation is progressively quenched in more massive galaxies and in denser environments. What are the main physical mechanisms able to moderate and stop star formation? An obvious one is the energetic feedback from AGN, where recently massive molecular outflows have been observed. Observational evidence will be shown with ALMA and NOEMA results. The mass outflow rate is estimated between 1-5 times the star formation rate. When driven by AGN, these outflows are therefore a clear way to moderate or suppress star formation. However, AGN feedback can be also positive, and evidence will be presented. Group and cluster environment can perturb considerably galaxies, quench their star formation, and transform their morphology in very short time-scales. I will present evidence of gas removal, where not only the external atomic gas is involved, but also inner molecular gas. Star formation still occurs in the tails, however with a much lower efficiency. The survival of dense clouds in harsh environments will be discussed.