The success of extragalactic infrared interferometry: from what we have learned to what to expect

Infrared interferometry has lead to a breakthrough in the investigation of Active Galactic Nuclei (AGN) by allowing to resolve structures on sizes of less than a few parsecs in nearby galaxies. Measurements in the near infrared probe the innermost, hottest dust surrounding the central engine and the interferometrically determined sizes roughly follow those inferred from reverberation measurements. Interferometry in the mid-infrared has revealed parsec-sized, warm dust distributions with a clear two component structure: a disk-like component and polar emission challenging the long-standing picture of the "dusty torus". New beam combiners are starting to resolve the kinematic structure of the broad line region and are expected to provide true images of the dust emission. Nevertheless, most AGN will remain only marginally resolved by current arrays and next generation facilities, such as the Planet Formation Imager (PFI), will be required to fully resolve out larger samples of AGN.