  Microlensing of gravitationally lensed quasars by the stars in the foreground
lens galaxy can be used to probe the nature of dark matter, to determine the
mean stellar mass in the lens galaxy, and to measure the internal structure of
quasar accretion disks. Until recently, little progress has been made toward
using microlensing for these purposes because of the difficulty in obtaining
the necessary data and the lack of good analysis methods. In the last few
years, both problems have been solved. In particular, Bayesian analysis methods
provide a general approach to measuring quantities of physical interest and
their uncertainties from microlensing light curves. We discuss the data and the
analysis methods and show preliminary results for all three astrophysical
applications.
