  Star clusters are among the first celestial objects catalogued by early
astronomers. As simple and coeval populations, their study has been
instrumental in charting the properties of the Milky Way and providing insight
into stellar evolution through the 20th century. Clusters were traditionally
spotted as local stellar overdensities in the plane of the sky. In recent
decades, for a limited number of nearby clusters, it became possible to
identify cluster members through their clustering in proper motion space. With
its astrometric data of unprecedented precision, the Gaia mission has
completely revolutionised our ability to discover and characterise Milky Way
star clusters, to map their large-scale distribution, and to investigate their
internal structure. In this review we focus on the population of open clusters,
residing in the Galactic disc. We summarise the current state of the
Gaia-updated cluster census and studies of young clusters and associations. We
discuss recent developments in techniques for cluster detection and age
estimation. We also review results enabled by Gaia data concerning the
dynamical evolution of gravitationally bound clusters and their stellar
inventory.
