Gravitational-wave detectors - LIGO, Virgo, and KAGRA - have revealed a population of massive black holes whose origin is still a subject of vigorous debate. Understanding the population of black holes in the Milky Way is therefore of key importance for understanding and putting into the astrophysical context the LIGO/Virgo/KAGRA discoveries.
Gravitational microlensing remains the only viable technique which enables us to detect and directly measure masses of isolated stellar remnants, especially neutron stars and black holes. In this talk, I will present the recent advancements in the field of gravitational microlensing, which have led to the discovery of the first isolated stellar-mass black hole in the Milky Way and which will pave the way for future similar discoveries. I will present how astrometric and interferometric observations of gravitational microlensing events allow us to detect and characterize isolated neutron stars and black holes. Finally, I will discuss whether black holes of different sizes can make up dark matter.
