A holder assembly comprises a first and a separable second part, the first part detachable from the second part, the first part comprising a tube and an environmental cell interface and the second part comprising an electron microscope interface, as a result of which the first part can be cleaned at high temperatures without exposing the second part to said high temperature.By forming the holder assembly from detachable parts, one part can be cleaned by heating it to a high temperature of, for example, 1000° C., clogging in the tubes can be removed by reduction of carbon, while keeping the other part (often comprising mechanical fittings, ball bearing, sliders, or such like) cool. The cleaning can be enhanced by blowing, for example, oxygen or hydrogen through the tubes.