A device for synthesising and studying compounds under controlled temperatures and pressures includes: a body delimiting a vacuum chamber including temperature-regulation means and vacuum-application means, and having one or more viewing windows enabling the inside of the chamber to be observed from the outside; temperature-regulation means that are intended for regulating the temperature inside the vacuum chamber; and vacuum-application means that are intended for regulating the pressure in the vacuum chamber; wherein it includes, inside the vacuum chamber, a sealed structure delimiting a sealed chamber having one or more viewing window facing said one or more windows in said body, and at least one pipe that is in fluid communication firstly with the inside of said sealed chamber and secondly with an outlet that is made in the body and provided in order to be connected to one or more sources of gas for synthesising said compound or sample.