The innermost regions of Young Stellar Objects as seen by VLTI/GRAVITY

Understanding how the protoplanetary disks around young stars are structured and evolve is crucial for star and planet formation theories. We observed in an homogeneous way several tens of Herbig Ae/Be and T Tauri disks with the VLTI/GRAVITY instrument in the near-infrared K-band. We aim at spatially resolving the sub astronomical unit region to gain a statistical understanding of their morphological and compositional properties, and at looking for correlations with stellar parameters, such as luminosity, mass, and age. Thanks to its spectral resolution coupled with high angular resolution, VLTI/GRAVITY allows us to probe the location of the warm and hot gas in the inner disk. In a near future, the GRAVITY+ instrument will have a drastically improved sensitivity that will give us access to a much wider sample of young stars, including lower-mass stars and younger embedded targets.