Schematic view of the innermost region of the CI Tau system. The sizes and their uncertainties derived from the GRAVITY observations are represented for the Brγ emitting region (blue circle) and for the K-band continuum (orange circle). The purple circle (and shaded area) depicts the truncation radius and its uncertainty derived from the GRAVITY Brγ emission line (Sect. 3.3). Additional characteristic scales associated with YSO are depicted: the sublimation radius (R_sub, pink line) for a range of absorption Q_R from one to four and the co-rotation radius (R_cor, green line). The stable-unstable magnetospheric accretion regimes are indicated with a boundary around 70% of the R_cor (Blinova et al. 2016).