Galaxies provide us with valuable clues on the large scale properties of the Universe in which they are embedded. Equally important, they tell us about the physical processes which are responsible for star formation
During the epoch of reionization the first stars and black holes in the Universe (re-) ionized the Intergalactic Medium. Studying the epoch of reionization will tell us about the first galaxies.
Observations of nearby galaxies and high-redshift quasars suggest that black holes are present in the majority of galaxies. The first quasars harbor already black holes as massive as several billion solar masses.