TEM/STEM cooling holders are mainly applied to investigate low temperature phase transformation and to observe the structure and elemental distribution of electron-beam-sensitive materials.

There have been traditionally two types of cooling holders:
        i) Holders using liquid nitrogen (LN2). The boiling point of LN2 is -195.8 °C so that the specimens can be observed at temperature down to approximately -180 °C.
        ii) Holders using liquid helium (liquid He). The boiling point of liquid He is -268.94 °C (or 4.21 K) so that the specimens can be observed at temperature down to approximately -250 °C.

Specimen cooling is one of the efficient common methods to reduce or even eliminate specimen contamination in TEM analysis. In this way, the mobility of the offending species (e.g. hydrocarbon molecules) is suppressed. However, specimen cooling causes some problems:
        i) Ice may form on the specimen. To avoid the ice formation, intermediate temperatures from -130 to 50 °C can be used.
        ii) Specimen drift.