An environmental conditioning assembly for use in mechanical testing at scales of microns or less. The assembly includes an enclosure housing with an environmental cavity therein. A sample stage is positioned within the environmental cavity and includes an option sample heater. The enclosure housing includes a cavity perimeter clustered around the sample stage, and the enclosure housing isolates the environmental cavity and the sample stage from an environment exterior to the enclosure housing. In an example, an expansion and contraction linkage maintains a sample on the sample stage at a static elevation according to heating or cooling fluctuations within the environmental cavity. A testing instrument access port extends through the enclosure housing into the environmental cavity.