Microlensing relies on the detection of a tiny deviation to the regular microlensing event light curve caused by the presence of a planet orbiting the main lensing star. The microlensing effect is sensitive to mass only and does not require the planet to be visible at all and it can probe mass and period regimes of planets not easily available with other methods. Therefore it is currently probably the only technique capable of detecting planets similar to Earth. However, the lower the mass of the planet, the smaller and shorter the deviation, hence very frequent and precise monitoring of on-going microlensing events is needed. IoA members are involved in the main microlensing survey, Optical Gravitational Lensing Experiment (OGLE) which constantly observes the Galactic Centre and finds almost a thousand microlensing events every year. Intensive follow-up of these events by other groups yielded discoveries of about a dozen planets, including one multiple-planet system.

The near-future Gaia mission will detect and alert on microlensing events from all over the sky and will provide additional opportunities for microlensing planets detections.