We present the development of a Nano-Reactor for in-situ studies of solid-gas interactions inside the Transmission Electron Microscope (TEM). This MEMS-based device acts as a multi-functional sample carrier and micro-sized laboratory for heating and gas experiments. Each Nano-Reactor consists of two Nano-Chips, which are sandwiched together to form a minimized chemical reaction chamber. The bottom Nano-Chip contains a four-point-probe micro-heater, which controls and introduces the heating environment (up to 1300°C) around the sample. The top cover Nano-Chip encases the gas while isolating it from the external environment, creating the closed Nano-Reactor. Samples are prepared directly onto the electron transparent windows which allow for the electron beam to pass through for in situ imaging. The thin windows, made of Si 3 N 4 , can sustain pressures up to 1.5 bar and high temperatures while ensuring low background atomic resolution imaging.