Our Galaxy the Milky Way is made up of a hundred billion stars. To truly understand its evolution we need to know exactly where we stand in this mass of constantly moving and changing celestial objects. To do this, Astrometry, the science of measuring the position, distance and movement of stars around us, is just about to take a giant leap forward with the launch of ESA’s new space telescope, Gaia. Gaia will make it possible to measure a billion stars of our Milky way