One of the main physics objectives of ITER is to operate, in a nuclear environment and on sufficient time durations, burning fusion plasmas, and thus demonstrate their viability for an efficient energy production. Besides the technology challenge, out of the scope of the present paper, magnetized plasma physics raises a series of issues that ITER will have the unique opportunity to address and solve. ITER is designed to confine a DT plasma in which α-particle heating dominates all other forms of plasma heating. This feature was never achieved so far by any experiment, and deserves specific studies and characterisation. ITER aims at producing a significant fusion power amplification factor (Q≥10) in long-pulse operation (~400s), at achieving steady-state operation of a tokamak (Q = 5) and, ultimately, retains the possibility of exploring “controlled ignition” conditions (Q≥30). Such goals require a dedicated scenario design activity which encompasses a number of physics elements such as heat and particle turbulent transport, influence of the magnetic configuration on transport properties, linear and non linear magneto-hydro-dynamics stability, operational constraints and control issues, including all burning plasma specific issues. Such elements will be detailed and illustrated over existing plasma tokamak discharges and physics and theory developments, giving a rapid overview of present fusion devices contributions in preparation for ITER’s plasmas.