The majority of analytical and empirical models used for the prediction of hydrodynamics and heat transfer behavior in two-phase gas-liquid flows are based on research data that were collected under terrestrial conditions. Under such conditions, where gravity plays a very important role in shaping the flow, empirical correlations used for the prediction of flow regimes, pressure drop, slip velocities and heat transfer rates, may not be adequately suitable for microgravity. One of the major applications of two-phase flows at microgravity conditions is the design and maintenance of active thermal management systems for future space stations and high-power communications satellites. Microgravity provides an ideal environment to study interfacial waves without the dominating effects of gravity. Studies of two-phase flows under microgravity conditions are also of great interest to better understand the behavior of terrestrial flows away from the masking effects of earth gravity.