This doctoral research is focused on the detection and characterization of short timescale astronomical variability, i.e. luminosity variations on timescale shorter than 12h, as part of the whole data processing and analysis for the European Gaia space mission. First I worked on the prediction of Gaia capabilities for identifying short timescale variability from Gaia photometry, by means of variogram analysis, and via light-curve simulations of various short timescale variable types. Then I investigated real Gaia photometry, looking for bona fide short timescale variable candidates from the first 22 months of Gaia data. This exploratory work resulted in a list of 3018 suspected periodic, short timescale variable candidates, published as part of the Gaia Data Release 2 (April 2018). Finally, I was also involved in various observational programs, contributing to Gaia transient events confirmation and open cluster photometric surveys. Moreover I explored the properties of the Deeming period search technique.