Our in‑situ TEM gas cell specimen holder enables the study of material behavior in gases at temperatures above 1000 °C, delivering atomic‑resolution imaging of gas–solid interactions under realistic reaction conditions. Gases or vapors are introduced through a microfabricated environmental cell using a compact, multi‑channel gas delivery system housed in a single chassis. Cell pressure is fully user‑controlled, from high vacuum to above atmospheric pressure. Local specimen heating is provided by an integrated MEMS heater with a calibrated temperature sensor, and the holder can be baked up to 160 °C for clean gas delivery. Custom data and image integration options are also available.