Astrophysical phenomena related to supermassive black holes : searching for local particularities in the center of the Milky Way and extragalactic nuclei at high angular resolution All projects aim at pushing the limits of our knowledge about the interaction between a galaxy and a supermassive black hole (SMBH) at its center. The development of a new instrument can be as valuable as combining different datasets. I follow both approaches and developed projects which deal with new instrumentation and telescope technology combine datasets from different wavelengths and resolutions and incorporate recent theoretical models and predictions which can be verified empirically. The first two of the six chapters compile astrophysical and technical background of the individual projects which are presented in the following four chapters. While the first project (Chapter 3) deals with observations of the innermost parsec of our Galaxy Chapter 4 presents data of the inner kpc of an active galaxy. The subjects of Chapters 5 and 6 are very luminous AGN host systems so called QSOs. Whereas Chapter 5 presents global spatially unresolved properties of SMBH host systems the radio jet analyzed in the final Chapter 6 combines all size scales. It is investigated from close to its origin out to several kpc. The accretion onto the black hole of the Milky Way (Chapter 3) is extremely inefficient and the SMBH possibly interacts dominantly via tidal forces only. The next discussed system (Chapter 4) is the prototype of moderately luminous Seyfert 2 AGN NGC 1068. Here a strong local influence of the nuclear X ray radiation is observed. Chapter 5 deals with the possible global importance of radiative interaction between highly luminous QSO AGN and the host. The radio jet in Chapte 6 definitely shows signs of interaction with the matter of its host several kpc away from the nucleus. Chapters 3 6 include a dedicated introductory and a conclusive section which put the results obtained in the larger astrophysical context of the observation ...