  This paper starts with a brief historical review about the PNLF and its use
as a distance indicator. Then the PNLF distances are compared with Surface
Brightness Fluctuations (SBF) distances and Tip of the Red Giant Branch (TRGB)
distances. A Monte Carlo method to generate simulated PNLFs is described,
leading to the last subject: recent progress in reproducing the expected
maximum final mass in old stellar populations, a stellar astrophysics enigma
that has been challenging us for quite some time.
