Observational results. Left: structure of FU Orionis as seen with the components of our NIR dataset. The outbursting region corresponds to the marginally resolved disk in the interferometric data. Right: (adapted from Armitage 2011): scenario of a FU Orionis outburst in the MRI-GI model. In the quiescent phase, the disk has a magnetically layered structure: material piles up at the outer edge of the dead zone due to GI. As it reaches a sufficient density and temperature to activate MRI, the full disk goes into outburst, which corresponds to the region seen in the NIR interferometric data. Locally, TI can be triggered very close to the star (<O.1 AU).