Rayleigh-Bénard convection (RBC) at high Rayleigh (Ra) numbers represents perhaps the most important model system to study heat and momentum transport by turbulent convection. Experiments reaching very high Ra, approaching values relevant for convective systems in Nature (like the flows in Earth's atmosphere or oceans), were performed using various working fluids, like cryogenic helium 4, or sulphur hexafluoride, in different laboratories, and provide unique insights into the dynamics of this `archetype of complex dynamical systems''.