The first wall and the divertor in present-day or next step thermonuclear fusion devices are exposed to intense fluxes of charged and neutral particles, in addition the plasma facing materials and components are subjected to radiation in a wide spectral range. These processes, in general referred to as `plasma wall interaction' will have strong influence on the plasma performance, and moreover, they have major impact on the degradation and on the lifetime of the plasma facing armour and the joining interface between the plasma facing material and the heat sink. Beside physical and chemical sputtering processes, thermal fatigue damage due to cyclic heat fluxes during normal operation and intense thermal shocks caused by severe thermal transients are of serious concern for the engineers which develop reliable wall components. In addition, the material and component degradation due to high fluxes of energetic neutrons is another critical issue in D-T-burning fusion devices which requires further extensive research activities. This paper represents a tutorial focussed on the development and characterization of plasma facing components for thermonuclear fusion devices.