This Small Business Innovation Research Phase I project will develop a microfluidic in-situ Transmission Electron Microscope (TEM) specimen holder with accurate temperature and pressure measurement and control abilities. The inability to dynamically image materials at atomic resolutions in changing liquid and gas environments is a significant impediment to the advance of physical, chemical, materials, biological and medical sciences. We have recently developed commercially viable continuous flow fluid sample holders for observations of interactions of materials in both liquid and gas environments at ambient pressures. These holders have already opened up new avenues of research in material reactions through real time observation and imaging of nanoscale material interactions. However, currently none of the results acquired with these systems can be quantified or verified because it is not possible in the current system to directly locally measure temperature and pressure in the microfluidic cell at the sample. This project will solve this problem by developing a new in-situ TEM microfluidic holder that contains microfabricated local temperature and pressure sensors inside the fluid cell. This will be a crucial enabling technique in opening up the possibilities of in-situ experiments while imaging at high resolution in fluids inside the TEM. The broader impact/commercial potential of this project is the availability of a characterization technique that can image solid/liquid and solid/gas interfaces with atomic resolution under quantifiable and accurately controllable environmental conditions. This product has the potential to becoming a high-impact in-situ TEM holder product, because it has a broad range of important applications over several scientific and engineering fields. It will allow biological structures to be imaged at nanometer resolution in their controlled native environment and provide new insight on structure-function relationships in biological systems. In materials science and chemistry it will provide new insight into the growth and synthesis of nanostructures under controlled atmospheric conditions, which is important for future generations of electronic devices. Finally, it will create insights for researchers studying catalysis under relevant and controlled environmental conditions, as well as new understanding of the fundamental processes in corrosion.