Microlensing and its Degeneracy Breakers: Parallax, Finite Source,
  High-resolution Imaging, and Astrometry
  First proposed by Paczynski in 1986, microlensing has been instrumental in
the search of compact dark matter as well as discovery and characterization of
exoplanets. In this article, we provide a brief history of microlensing,
especially on the discoveries of compact objects and exoplanets. We then review
the basics of microlensing and how astrometry can help break the degeneracy,
providing a more robust determination of the nature of the microlensing events.
We also outline prospects that will be made by on-going and forth-coming
experiments/observatories
