The apparatus is for use with an electron microscope, a sample, a source of high pressure gas and a vacuum pump system. The apparatus includes a holder part a body part and a Joule-Thomson refrigerator. The holder part is adapted to receive the sample and adapted to present the sample to the microscope for inspection in use. The body part defines a cavity, the cavity being evacuated by the vacuum pump system for use. The refrigerator is disposed within the cavity and thermally-coupled to the holder part, the refrigerator being coupled in use to the source of high pressure gas to maintain the sample at about a predetermined temperature.