Stellar and gas dynamical studies in an ever-increasing number of galaxies have established 
that many -and perhaps all- luminous galaxies contain central supermassive black holes (SBHs). 
Following the discovery that the SBH masses correlate with various properties of the host galaxy 
-such as bulge luminosity, mass, velocity dispersion, light concentration, and halo circular velocity- 
it has become widely accepted that SBH and galaxy formation are closely entwined.
More recently, a large imaging survey with the Hubble Space Telescope has shown that 50 to 80% of 
low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, 
regardless of host galaxy morphological type. I will discuss the connection between stellar nuclei, 
SBHs and host galaxies, and argue that a generic by-product of galaxy formation is the creation 
of a central massive object (CMO) -either a SBH or a compact stellar nucleus- that contains 
a mean fraction, ~0.2%, of the total galactic mass. In galaxies with masses greater than a few 
tens of billion of solar masses, SBHs might be the dominant mode of CMO formation.