"The purpose of the proposed project is to study the host galaxies of active galactic nuclei. AGN are considered to be among the most energetic processes in the universe and are thought to affect the evolution of galaxies. Because of their vast energy release they often outshine their host galaxies, so the study of the AGN-host system can be very challenging. Here, we propose a multi-wavelength approach, taking advantage of the fact that different physical processes leave their characteristic signatures in different parts of the spectrum, for example hot gas being accreted onto the AGN dominates the X-rays and UV light, while star formation and stellar emission of the host galaxy have their peaks in the far-infrared and optical bands respectively. We are planning to use a sample of AGN from the regions of the sky with the deepest coverage in virtually all bands, the Chandra deep fields. New telescopes and instruments like NuSTAR, SCUBA-2, and Herschel, for which the host institute will guarantee data flow, will provide an unprecedented multi-wavelength dataset and we plan to develop new SED fitting methods to exploit it. SED fitting is one of the most promising methods to disentangle AGN and host galaxy properties, and it uses combinations of template SEDs (spectral energy distributions, i.e. broad-band spectra) of different physical processes to reproduce the observed spectrum. We plan to expand on a code developed by the researcher and ultimately make it available to the astronomical community. The results will be used to study the coeval growth of the AGN and its host, taking into account information on different processes taking place, and their interactions. This will help us understand the importance of AGN for the development of the structures we observe in the universe today."