Excitation frequencies in the terahertz (THz) range are expected to lead to functionally relevant domain movements within the biological macromolecules such as proteins. The possibility of examining such movements in an aqueous environment is particularly valuable since here proteins are not deprived of any motional degrees of freedom. Small angle x-ray scattering (SAXS) is a powerful method to study the structure and domain movements of proteins in solution. Here, we present a microfluidic cell for SAXS experiments, which is also transparent for THz radiation. Specifically, cell dimensions and material were optimized for both radiation sources. In addition, the polystyrene cell can be 3D printed and easily assembled. We demonstrate the practicality of our design for SAXS measurements on several proteins in solution.