Gaia, Pan-Starrs, the LSST (Large Synoptic Survey Telescope) or SKA (Square Kilometer Array) are projects that will leave after completion massive legacy archives with sizes ranging from petabytes (1015) to exabytes (1018) (or even zettabytes (1021) in the further future). These databases will undoubtedly harbour scientific information that astronomers must uncover to bring it into the form of knowledge and new discoveries. In order to do so, we will need to combine the traditional analysis techniques with new statistical techniques borrowed from the fields of Data Mining and Knowledge Discovery. In this seminar I will intend to provide a global overview of the techniques that will be of particular interest for the scientific exploitation of Gaia, while at the same time, emphasizing the basic concepts of the field.