  Over the last decade, HST imaging studies have revealed that the centers of
most galaxies are occupied by compact, barely resolved sources. Based on their
structural properties, position in the fundamental plane, and spectra, these
sources clearly have a stellar origin. They are therefore called ``nuclear star
clusters'' (NCs) or ``stellar nuclei''. NCs are found in galaxies of all Hubble
types, suggesting that their formation is intricately linked to galaxy
evolution. In this contribution, I briefly review the results from recent
studies of NCs, touch on some ideas for their formation, and mention some open
issues related to the possible connection between NCs and supermassive black
holes.
