The second Gaia data release has published high-precision astrometric measurements for over a billion sources. In the coming years, Gaia data will make fundamental contributions to numerous open questions on the evolution of our Galaxy. We here focus on the long-standing debate on the origin and dynamical nature of the warp of our Galaxy, with particular attention to the warp-induced motions in stellar kinematics. Taking advantage of Gaia DR2 data, we detect the kinematic signature of the Galactic warp out to a distance of 7 kpc from the Sun. The signature manifests itself as a gradient of 5-6 km/s in the vertical velocities from 8 to 14 kpc in Galactic radius, with a signal-to-noise larger than 10. The signal is present in two samples of intrinsically young and old stellar populations, selected via a probabilistic approach. Based on our results, we argue that the warp is principally a gravitational phenomenon, thus placing an important constraint on the possible formation scenario.
Finally, we observe that the old stellar populations present a smooth signal, as expected from a dynamically relaxed population, while the young sample exhibit a strongly perturbed kinematic pattern
