  Ongoing microlensing surveys have already yielded more than five hundred
microlensing events, most of which have been identified in real-time. In this
review I present the basic theory and observational status of these surveys. I
highlight the discoveries made so far - these include constraints on the dark
matter content of the Galaxy, the structure and mass function of stars in the
Galactic bulge and applications on stellar atmospheres and populations. I also
briefly discuss the scientific returns (such as planet detection) from
real-time photometric and spectroscopic follow-up surveys. With improved
software algorithms and more powerful instrumentations, the number of
microlensing events will be greatly increased in the future; the Space
Interferometry Mission, on the other hand, provides the possibility to break
the lens mass and distance degeneracy. I conclude that microlensing is
developing into an exciting technique with diverse applications.
