Supermassive black holes (SMBHs) have become an integral part of modern galaxy evolution models. A major milestone was the discovery of scaling relations between SMBH masses and host galaxy properties, observed locally. While the origin of these relations and their evolution with redshift remains controversial, feedback from accreting SMBHs (i.e. active galactic nuclei) has been suggested as a likely regulating mechanism, linking SMBH and galaxy growth. I will discuss open questions regarding SMBH scaling relations and highlight the advantages of 3D spectroscopy for probing SMBHs through spatially-resolved studies of gas and stars in the surrounding host galaxy. I will present results from our recent/ongoing projects, in which we analyze SMBH masses, accretion, and feedback based on 3D spectroscopy in the optical, near-infrared, and at millimeter wavelengths.