Volatiles (such as H2O and CO2) are crucial components on our planet, determining an environment at its surface where life can prosper. However, these volatiles are also present in the Earth's interior, governing global geodynamics and the chemical evolution of the mantle through melting. Laboratory experiments recreating the high pressures and temperatures of the Earth's mantle provide unique insights into the behaviour of volatiles and volatiles-induced melting processes at these extreme conditions. In this seminar, I will discuss the distribution of H2O between minerals and melts determined in hydrous and hydrous-carbonated systems at the bottom of the upper mantle. These data are used to investigate the formation of volatile-bearing melts that are seismically detected in this region. In addition, in the last part of the seminar I will also use these data to discuss the H2O content of mantle minerals found as inclusions in some natural diamonds.