  Feedback from active galactic nuclei (AGN) on their host galaxies, in the
form of gas outflows capable of quenching star formation, is considered a major
player in galaxy evolution. However, clear observational evidence of such major
impact is still missing; uncertainties in measuring outflow properties might be
partly responsible because of their critical role in comparisons with models
and in constraining the impact of outflows on galaxies. Here we briefly review
the challenges in measuring outflow physical properties and present an overview
of outflow studies from high to low redshift. Finally, we present highlights
from our MAGNUM survey of nearby AGN with VLT/MUSE, where the high intrinsic
spatial resolution (down to $\sim$10 pc) allows us to accurately measure the
physical and kinematic properties of ionised gas outflows.
