Abstract
Active Galactic Nuclei (AGN), found at the dynamical centers of about
10% of all galaxies, are among the most energetic phenomena in the
Universe. AGN are extremely compact, comparable in size to our solar
system, yet they can produce more radiation than all of the stars in a
galaxy. The power source for AGN is accretion of gas onto a super-
massive black hole, which efficiently converts a significant fraction
of the rest mass energy of accreting gas into radiation. Not all
accreting super-massive black holes are so energetic, however, and
those that do not produce much radiation are called Low-Luminosity AGN
(LLAGN). I will discuss the properties of LLAGN, paying particular
attention to those objects that are much fainter than simple accretion
models would predict. I will present X-ray observations of a number
of LLAGN, including high resolution X-ray spectroscopy of M81, and
show how these observations can be used to uniquely study the hot
accretion flow close to the black hole. Furthermore, combining the X-
ray data with multi-wavelength observations provides a powerful tool
to study the accretion physics. We certainly don't have a complete
understanding of LLAGN at present, and I conclude by presenting some
of the challenges that lie ahead.