  Foundations of standard theory of microlensing are described, namely we
consider microlensing stars in Galactic bulge, the Magellanic Clouds or other
nearby galaxies. We suppose that gravitational microlenses lie between an Earth
observer and these stars. Criteria of an identification of microlensing events
are discussed. We also consider such microlensing events which do not satisfy
these criteria (non-symmetrical light curves, chromatic effects, polarization
effects). We describe results of MACHO collaboration observations towards the
Large Magellanic Cloud (LMC) and the Galactic bulge. Results of EROS
observations towards the LMC and OGLE observations towards the Galactic bulge
are also presented. Future microlensing searches are discussed.
