Discovering a new state of matter is always a major event for the scientific community. As the science moves forward, those new states are always more difficult to discover andand need increasing effort to be understood. The field of nuclear physics does not make exception to this rule: more then 30 years ago, it was predicted that a so-called quark-gluon plasma could be achieved in ultra-relativistic heavy ion collisions, the prominent feature of this statebeing that the fundamental constituents of hadrons would to be deconfined. Since then, its quest has generated a considerable interest both from the experimental and theoretical viewpoints.Nevertheless, many of its properties are still only partly understood. One of the main difficulties encountered when aiming at characterizing such QGP state is its very short lifetime, of the order of 10 fm/c. This obviously forbids the use of external probes. One has to rely on particles produced within the QGP itself to characterize its features and quantify its properties. In this talk, we will concentrate on what we could learn from heavy quarks observables, like the production of D and B mesons or J/psi and upsilons. In particular, we will focus on the question of the quenching of open heavy flavours.