After a long a glorious history, marked by the first direct proofs of neutrino existence and of the mixing between the first and third neutrino generations, the reactor antineutrino experiments are still well alive and will continue to give important contributions to the development of elementary particle physics and astrophysics. In parallel to the SBL experiments, that will be dedicated mainly to the search for sterile neutrinos, a new kind of experiments will start playing an important role: the medium baseline reactor experiments, aiming to study the neutrino mass ordering. The first example of this kind, the liquid scintillator JUNO experiment, characterized by a very high mass and unprecedented energy resolution, will soon start data taking in China. Its main aspects are discussed here, together with its potentialities for what concerns the mass ordering investigation and also the other issues that can be studied with this detector, spanning from the accurate oscillation parameter determination, to the study of solar neutrinos, geoneutrinos, atmospheric neutrinos and neutrinos emitted by supernovas and to the search for signals of potential Lorentz invariance violation.